Sudden Power Loss on Full Throttle

When I accelerate on full throttle I often get a sudden loss of power higher up the revs. It only lasts a second or so and it feels like I have lifted off the throttle completely then slammed my foot back down.

I recently replaced the earth cable from battery to chassis with one which is a little longer. I checked the earth strap from chassis to gearbox and it's in fine condition with no fraying or broken strands.

I've put a post up on our facebook group and had some good suggestions but know there are lots on here who don't use FB, so it'd be good to get extra input

When you loose power do you see an injector light at all?

Yes, check for codes even if the injection light isn't on. Otherwise, usual suspects... change plugs if not done in last year or so, maybe try swapping out coil packs and airflow meter.

Also check the ECU chip is seated firmly (remove and refit) especially if it's on a protection board that hangs out of the socket.

And if you haven't already bypassed the YCOD I'd do that now.

Also Chris as mat said,check your boost hoses.

If you're seeing an injector light when it cuts power it might be a knock sensor is picking something up.

Assume all gentle/medium acceleration is ok?

Thank for the quick replies all!

I have never experienced this on light throttle / around town, only on full throttle. The car does not backfire at all when this happens.

I don't think I get an injector light, although it happens so fast so I can't be sure I'd see it even if it was there.

I will start by bypassing the YCOD, reseat my GTEC 2 that I fitted last year and check all my boost pipework.

Then if it's still doing it will work out how to get Startrek set up on my mac and go through the codes. Then go through switching out parts.

Thanks again all for the input.

How much fuel do you have in the tank? I find that prolonged full throttle with anything less than 1/3 of a tank is enough to cause fuel starvation.

However, I think you'll find it's the ECU that's backing off the boost due to something that's given it cause for concern

I had nearly the same thing going on. But mine was happening when coming off full boost and throttle.

As it happens it turned out that I had a couple of faults. Elephant boost hose cracked and the Maf connections.
I noticed the prongs on the Maf plug had oxidized both male and female. Mine does sit around a lot in the garage.

I gave them a scratch to free the oxidisation then a clean,also cleaned the Maf with carb cleaner then an airline.

I am running with half a tank of V Power, this has been an issue even with a full tank, however I fill up once a month max, sometimes longer between fills. She's about to go back into daily use so want her running right and this has only come about in the last 2 weeks or so.

I will give the elephant trunk a look over, although was replaced about 3 months ago so I'll be peeved if it's ripped again! Will also take a look at the MAF connections, thanks all.

Are you running the fuel pump direct feed mod?

Yes, I bought 'Jap's' kit many years ago.

Had exactly the same problem - mine turned out to be the MAF connector as mentioned.

I had the same problem but at random rev ranges, decided to re-wrap my coil pack wiring and on the last one I noticed the cam cover earth wire was loose.
problem solved.

Thanks Simon.

Will also check the coil pack wiring, thanks Patrick.

Ok so this afternoon I have:

Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated my GTEC 2

Bob has suggested to check the hard pipe before Inlet manifold which I'll do before putting it through its paces tomorrow.

Thanks all for the advice!

Try swapping out the two relays on the passenger side one is the fuel pump.
Don't forget what Joe (cc) said about the knock sensor.

The fuel pump relay on mine failed intermittently. But it failed when I was coming up to stop for road junctions etc( low revs)

Silly question, where can I buy replacement relays that you are referring to? Electrics are really not my thing!

They are a common part Chris. I imagine any car part shop.

Cheers Joe!

I did this:

Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated my GTEC 2

However got to open her up and is still cutting out.

I will try and get the codes read, does anyone know if Startrek will work on a macbook? I will also get those relays switched out for new ones over the weekend and check the hard pipe before inlet.

Do you have a boost gauge? If so, what's the boost doing when it misfires? If not, would be worth fitting one even temporarily with a hose in the window and gauge taped to the dash.

Pretty sure Startrek is PC only.

If you don't find any stored codes it's probably time to start swapping out bits with known good ones. Fuel pump and main injector relay at ECU, then airflow meter + coil packs. Also change spark plugs if they haven't been done relatively recently.

Can be hard to track this kinda thing down if no error code showing, could be a sensor fault or a wiring fault or fuel pump or ECU or hidden boost leak.

May also be worth trying with the standard chip if you still have it (if not I can send you one if you drop me a PM with your address), in case there's some underlying problem with fuelling and the extra ignition advance in the Gtec2 is causing knocking. Would also help to point towards boost/fuelling/ignition type issue or just a sensor/wiring problem.

And are you using a boost controller (manual or electronic) or just the standard EBV?

Mine was my ebv was causing misfire and slight hesitation ..put the standard darlek back on and sorted everything was fine...

What is your Turbo Chris? Standard?

Startrek is PC only but if someone could download/install a Virtual Box for you .......

If you're attending http://www.thedepartureloungecafe.co.uk/ meet on the 7th Oct I will bring my laptop and cables Chris

My turbo is standard, I have an electronic boost controller running 17psi max boost on my boost gauge.

When this happens the boost level drops and the Car slows down with the revs dropping appropriately. Then everything returns to normal. It’s as if I lift off the throttle and then smash my foot back down immediately.

This so similar to what I had. I found two split boost pipes which I replaced,I cleaned the icv and cleaned the Maf.

If you have no split pipes then I'm wondering if one is collapsing ? Then returning to shape.

What about the air doughnut pipes?

Try cleaning the boost controller solenoid with carb cleaner, or if you have one fit a PRV @ 1.2 bar just to rule out a problem with the boost controller/valve.

Could also be split boost pipe as said, with the split only opening occasionally.

Check the lower side of the hose between the hard plastic pipe beside cam cover and the throttle. Wipe around the hose with a white paper towel and if you pick up a lot of oil residue that'll be the split, as the air contains oil from the intake oil breather system. Intake sleeves at plenum could also be split although not easy to check around the back.

I went to my local motor factors and the relays were £25 each! So I've ordered 1 of them and will switch out individually.

I will double check for split boost pipes, I do hope thats the cause as it's a relatively simple fix.

I'll see if I can find my old PRV in the loft, I'm sure it's up there somewhere and try and rule out the EBC.

All donut inlet pipes were replaced in 2011 with new Fiat items, so I'd hope it's not those.

I"ll clean out the boost controller solenoid as well.

I vent to atmosphere the oil record so there is no oil vapour in my inlet pipes.

Thanks again for the input!!

Ok jobs done today:

Cleaned inside of EBC solenoid with contact cleaner
Checked hard inlet pipe metal collar whose metal collars are in correct position
No boost splits for pipe just before inlet and just before inlet hard pipe
Replaced 24” battery negative strap with 12” item as per OEM length

Will report back after I open her up next week, thanks again all.

I missed this on my first pass, thanks for the offer however I can’t make that event.

I have a fair few laptops lying around with windows on.

I have wanted to find a use for them, so I will set one or two up with all the startrek variants.

I got my dates muddled I’m in! If it’s not resolved I’ll gladly take you up on your offer Richard, thanks.

I do hope you get it sorted - but I will be there with all the gubbins

OK she's still doing it. So the jobs I've done:

Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated my GTEC 2
Cleaned inside of EBC solenoid with contact cleaner
Checked hard inlet pipe metal collar whose metal collars are in correct position
No boost splits for pipe just before inlet and just before inlet hard pipe
Replaced 24” battery negative strap with 12” item as per OEM length
Replaced 1 of the 2 fuel pump relays.

Are there any other suggestions? If not I'll get the codes red by BBR on 7th Oct and go from there.

Checked both positive and negative battery connections- in case they are loose?

Check connections to and around starter motor?

Getting codes checked is good logical next step.

Have you checked all the earth strap connections ?

Other than getting the codes read ASAP I think I'd be starting to swap things out to eliminate them at this point. Standard chip, PRV @ 1.2 bar, Airflow meter, coil packs, spark plugs to name a few.

You can swap any bits off mine at the meet if you like.
I have GTEC1 chip - but could probably dig out my standard chip if necessary.

Both battery terminals are on tight.

I will check starter motor, begin to switch out parts and get codes read. I still have my original chip so will start there before robbing BBR of some of his parts next weekend

Today I ran with base boost ~8psi and no matter how hard I tried, it did not cut out. Does this tell me anything eg the spark plugs / coil packs ok?

Does your car still have a plastic dump valve....???

It could still be the plugs or coil packs, if the spark is weak it can still fire OK at low boost but not at full boost.

I have run with no dump valve for a few years now so it’s not leaking there...!

Will check the history of the spark plugs and replace, it’s easier to swap coil packs in a pub car park than sparks as well!

Spark plugs last changed in 2013 and 7,000 miles ago, will get them changed!

The sparks were changed today and number 3 looked in poor condition vs the rest and number 3 coil pack was split. Replacement coil pack on order!

Also took the time to fit a replacement rocker cover gasket - I've had it in the boot for months!

I drove to the breakfast club meet this morning and she still has the sudden power loss, but it does not seem to be as severe as it was previously.

Richard brought along his laptop and Startrek and we read the codes on my car, the only one which showed up was:

(63) Lambda integrator FR upper limit

Does anyone know what this means?!

FR upper limit is usually caused by a faulty MAF sensor, give the MAF sensor a clean with some aerosol brake cleaner.

I have it a cursory spray with electrical contact cleaner in the intake pipe, but will remove the sensor and give it a proper soaking.

startrek image from today Chris

Although I think I may be a little late lol

No image ?

Erm what did I say about the Maf?

https://www.dropbox.com/home/Public?preview=Gunzi_T431OKE_v2.JPG

As well as ...

Boost hoses
Elephant boost hose cracked
Maf connections
Fuel pump relays
Knock sensor
Turbo? Standard?
Split boost pipes
Clean icv
Clean maf
Collapsing pipes
Doughnut pipes

Lol

Not just a cursory spray clean.
But thanks blue boy for reminding us that I have been trying to help Chris.

I get a bit lost between this thread and the 3-4 posts on Facebook however previously I did follow your instructions for cleaning off the actual MAF connector. I then sprayed into the MAF housing, through the plastic mesh, with contact cleaner however tomorrow will remove the sensor and give it a damn good soaking.

I don’t have an airline but the car will not be driven until Monday so should evapourate in that time.

I’ve been putting it off as one of the security Allen bolts that hold the MAF sensor into the pipe work is rounded and a complete arse to remove!

I see your problem Chris. I left mine in its tube. Cleaned it with the carb spray. Then the airline.

It could be that yours is just fubared.
Have you run the car with the Maf disconnected?

Will give that a try and see what happens. Cheers Joe.

I would be tempted to close the spark plug gap down slightly - say 0.6mm instead of the usual 0.7 (this only works if you're running single-electrode plugs)

Don't think anyone has asked the question yet - what plugs are you using?

I replaced my NKG 6's with Bosch FR6KTC, these are triple electrode plugs.

Do you still have the old plugs? If so, it would be worth fitting them, just to see if it makes any difference at all - this would confirm or eliminate plugs as a culprit

I went from having the issue with the old plug to switching to the new plugs this weekend and still having the issue albeit not as severe. Plug 3 was in poor condition and coil pack 3 was split.

Replacement coil pack will be fitted tomorrow and go from there.

Well she's still doing it, current list of tested, checked and replaced:

Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated my GTEC 2
Cleaned inside of EBC solenoid with contact cleaner
Checked hard inlet pipe metal collar whose metal collars are in correct position
No boost splits for pipe just before inlet and just before inlet hard pipe
Replaced 24” battery negative strap with 12” item as per OEM length
Replaced 1 of the 2 fuel pump relays
Replaced spark plugs with Bosch FR6KTC
Replaced 1 x coil pack which was split

Jobs still to do:

Switch out boost controller to PRV
Switch out GTEC 2 to standard chip
Switch out other fuel pump relay
Run with no AFM connected
Soak AFM in contact cleaner
Bypass other YCOD cable
Check Fuel pipes in engine bay dry and tight
Breather hose deforming at high revs/pressure?
Compression test
Check wiring to starter motor / alternator
Check all fuses

Any other thoughts?

Is she still doing it, but not as bad/just as bad?

Someone more savy then me will have more insight- but if sounds like an electrical gremlin rather then anything else. Maybe in the wiring to the injectors on the plenum-or another area exposed to the heat of the engine? Hard to track I know.

It strange that its only at full revs though...

You certainly are doing the right thing in being as methodical as you can at trying to resolve this.

Random thoughts:

Fuel pipes in engine bay dry and tight?
Fuel pump giving up ghost/filter blockage of some type?
Breather hose deforming at high revs/pressure?
Good new/clean air filter in place?
No water into/issues affecting ecu?

Its interesting your getting it flat out...when everything else is at max stress.


MM

Thanks MM, I will check all.

Air filter was replaced in 2014 with Apexi, and done about 6k since then. I'd hope it is not blocked yet!

ECU was dry when I reseated my GTEC 2.

I'll also get the other yellow connector of death cable bypassed.

A chap at my work has a compression testing kit so will give that a go next week whilst crossing fingers toes and every other part that is crossable.

I'm clutching at straws a little now, but how old is your battery?

I'd swap out the airflow meter for a known good one rather than try any more cleaning. If it's dodgy then all the cleaning in the world won't help and sometimes too much cleaning can actually break them.

Also check your pipework where you removed the dump valve and sealed the holes, could be leaking there. Or re-fit the old dump valve + pipe if you still have it, just for testing.

May also be worth using cables ties to tightly secure the airflow meter and throttle position sensor connectors, just in case.

OK I did nothing to the Coupe over the weekend as wanted it 'off' but today took a mate out to film the issue.

I have yet to work out how to link into Flikr, so here are the direct links which I bloody hope work!

https://flic.kr/p/Z6vooy

https://flic.kr/p/ZrsFe5

In short:

The boost drops from 17 psi to 9psi then shoots straight back to 17 psi.

The revs drop off the dial from 3.5 k to 1.0k before rising again to 3.5k.

So I'm thinking this could be linked to boost controller for the boost issue but I cant explain the rev gauge that is truly bizarre!

Electrical on the ignition side by the looks of the Rev counter engine won’t fluctuate that quickly

Yes, that surely has to be an electrical rather than boost/mechanical issue.

Bad power or ground connection somewhere, or ignition switch fault or ECU fault maybe?

Have you cleaned and tightened all ground points? I'd also try wiggling the main engine loom connector behind the battery even just while the engine is idling, to see if anything happens. Maybe replace the rest of the coilpacks too, I wonder if a dodgy coil could be pulling down the supply voltage to the rest. And double check all the coil pack wiring again.

I have a spare reset ECU if you want to give that a try, just drop me a PM.

Thanks for the input chaps this has changed the direction of my testing. Will give a few a try over the course of the week.

I wiggled the cable behind the battery and also checked the loom which runs drivers side into the car for damage and the wiggle test. The car behaved normally so cutting out.

https://flic.kr/p/Za3BbN

I had previously checked the battery ground and the chassis ground which locates to the same point.

I recently replaced the battery negative cable and retained the original chassis earth cable which both go to the same point into the chassis. So it now looks like this, with 1 cable stacked on top of the other:

Pull and re-seat all the fuses and check around the fuse box and maxi fuses for heat damage or corrosion. Also check ECU socket and plug for water damage or corrosion if you didn't already.

Strange that it only happens on full boost... so is that a vibration/movement issue with dodgy wiring or an electrical problem with something cutting out at high load?

If you PM me your address I'll send you a spare ECU for testing, would be good to eliminate that before going hunting for wiring issues which could be just about anywhere.

I found a melted fuse, green 30 amp behind the battery. Now replaced!

Will send you a PM, thanks Graham.

Which 30 amp green fuse? The big maxi fuse in the small fuse box behind battery or the small 30 amp fuse in the pair with no cover?

Maxi fuse is the EFI fuse which supplies the ignition and ECU, the small one is just for the internal fan blower. Not uncommon for the small one to melt so my guess is it's that one and it's most likely not related to the power loss issue, but if it's the maxi fuse that's melted that might explain something!

I've sent the reset ECU now so hopefully that will at least help with diagnostics.

It was the small 30 amp fuse in the pair with no cover and I did test it but yes you were correct I still have yes I still have the issue!

Gunzi,

Was the car doing any of this this before you replaced the earth strap? If so when did it start doing it?

Had you done any work/had the car off road before hand?

Also- is your battery still locked in place on the tray?

Sounds like something -maybe small is loose/ moving around under that acceleration.

Wonder if a go pro would capture whats going on under the bonnet? You may see sparks fly...!

MM

I also suspect this started to happen after I replaced the earth strap, but I’ve tried 2 different ones and it still does it.

That said the earth straps are stack on one another rather than going into the same connector.

Will double check the battery is secured.

The battery read 14.x volts during code reading so likely needs replacing.

All work is logged will dig it out and post up 2017.

I don't envy you with this one Chris- but just imagine the sense of achievement you are going to get when you finally get to the bottom of it!

A new suggestion

Run a separate earth strap from the battery to a new location somewhere on the engine and also to a new location on the chassis

As a temporary measure to test the theory, you could just use a decent jump lead. You should do these one at a time - battery to block first, then battery to chassis

Shame you're so far away - I could lend you a good set of coilpacks (I suppose I could always post them....)

Without reading back over two pages - have you had your ECU codes read?

Cheers Pete and Nigel.

Nigel good suggestion I’ll try the jump lead idea.

I got the codes read and had 1 code was:

(63) Lambda integrator FR upper limit

Thanks for the offer of coil packs. Will keep you posted.

Graham has sent me a spare ECU to try as well.

So tomorrow and Saturday it’s

Compression test
Switch ECU
Junp lead test

And cross fingers!

That could be the problem, the original earth strap clamp is bolted down to fresh metal in the factory, if you've connected to the exposed side of the clamp or the exposed cable it'll be corroded and may not give a good low resistance connection and so might break down under high load.

Try cleaning up the connection point until it's shiny and getting the biggest/tightest clamp area against it that you can. Or just drill and tap a new hole for the new cable and secure with a new bolt.

Or maybe the new cable has a crap high resistance connection to the connector at the battery end... how does the actual cable join to the connector there, solder/weld, crimp or screw? And is it square and tight to the battery terminal?

Your getting warmer Gunzi-keep going!!

keep them crossed, don't make them cross lol

Today I did the following:

Switched ECU with one from GrahamL (thank you!)
Replaced other yellow connector of death with spade connections
Checked the battery is secure
reseated every fuse under the bonnet and in the fuse box



Went out for a drive and there was no difference the car still cut out exactly as per the earlier video.

When I got back inspected the earth strap to chassis connection. My observations were:

1) The battery earth strap was next to the chassis with the gearbox strap on top of the battery strap
2) The battery earth strap had red insulation tape which was sandwiched down by the gearbox chassis strap - slightly separating the 2 earth connections. Which you can just about make out from this photo:





This was the red tape which shows it was being squashed:



and after trimming:


I cleaned up the chassis connection:



This was the condition of the original gearbox to chassis connection:


I sanded down all connections so they were shiny. It was reassembled with gearbox connection next to chassis and the battery to chassis on top of the that (opposite to when I removed it).

I ran out of time to take it for a drive however will test it tomorrow.

So now the list looks like this:

Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated my GTEC 2
Cleaned inside of EBC solenoid with contact cleaner
Checked hard inlet pipe metal collar whose metal collars are in correct position
No boost splits for pipe just before inlet and just before inlet hard pipe
Replaced 24” battery negative strap with 12” item as per OEM length
Replaced 1 of the 2 fuel pump relays
Replaced spark plugs with Bosch FR6KTC
Replaced 1 x coil pack which was split
Bypass other YCOD cable (connector now removed from car)
Check and reseat all fuses in engine bay and fuse box
Switched ECU (thanks GrahamL)
Rewire earth connections and trim excessive insulation

If the latest doesn't solve it then jobs still to do:

Switch out boost controller to PRV
Switch out GTEC 2 to standard chip
Switch out other fuel pump relay
Run with no AFM connected
Soak AFM in contact cleaner
Check Fuel pipes in engine bay dry and tight
Breather hose deforming at high revs/pressure?
Compression test
Check wiring to starter motor / alternator

Good luck and fingers crossed...interesting to watch this unfold ...although I'm sure interesting is probably not the word you would use 😵

Cheers rayzer82.

I am a patient chap, I know a number of other people who'd have stuck a hammer through the block by now

You're not kidding....

The rest of the world is watching

Did you check the condition and tightness of the earth strap on the back of the engine near the bottom of the triangular bracket? Also the bottom bolt on that bracket has to be tight to make a good earth connection from the bracket to the engine.

Just that bottom bolt being missing (which isn't even directly part of the earth strap to bracket) can be enough to cause ECU failure and non-start.

You'll probably need to remove strut brace to get an arm down there, or maybe you can check it from below.

I didn’t realise there was a connection down there.

I have minor oil leak I need to sort out and will remove the undertray to inspect so could kill two birds.

Yup, there are 6 ground points in engine bay:

1. Front left, on chassis leg near alternator
2. Front right, on chassis leg in front of battery (opposite to #1)
3. Front right of gearbox (cable continues from #2)
4. Right side under coil pack cover
5. Back right of engine bay near strut top mount next to ABS diagnostic socket
6. Rear of engine near bottom of large triangular support bracket

#6 is important as it's the first ground connection from the ECU in the loom into the engine bay. You can probably reach it from below without removing the undertray, or it's at max reach from above with the strut brace off.

Maybe the bolt on the ground strap there is loose or it's corroded, or the bottom bolt on the bracket could be loose. The two top bolts on the bracket don't provide a ground connection as they're insulated by vibration dampers.

ok I went for a drive and it still doing it.

So as for what's been checked on the ground connections:

1. Front left, on chassis leg near alternator Checked
2. Front right, on chassis leg in front of battery (opposite to #1) Checked
3. Front right of gearbox (cable continues from #2) Checked
4. Right side under coil pack cover Checked
5. Back right of engine bay near strut top mount next to ABS diagnostic socket
6. Rear of engine near bottom of large triangular support bracket

I will get under it tomorrow and check the rest. I am also going to find someone who has the original battery to chassis / gearbox cable to be able to return it to original to test.

Here is what's been done this year:

2017

Resprayed drivers and passenger door, rear bumper, removed dent in boot and dent in passenger rear ¾ 20/1/17 @ 136k
Car seat for Rafa 27/1/17 @ 136k
Replaced cracked sump with used unit, 2 x AD08R on rear (rears swapped to front) Millers CFS 10w/60 oil, N/S drive shaft gaiter & 2 rear number plate bulbs, handbrake console, smooth screw cap for door card, drivers window rubber, drivers door seal, scuttle screw & headlamp main beam backing 24/3/17 @ 136k
Resealed inside both doors weather proofing with flashing tape to maintain water seal and sound deaden the doors 15/4/17 @ 136k
Replaced Elephant trunk inlet pipe to turbo with used item 4/6/17 @ 136k
Fitted allen key bolts to undertray to secure it correctly at the front 4/6/17 @ 136k
Removed door check strap for welding 11/7/17 @ 136k
Replaced all dump valve blank and oil recirc rubber bungs with Stainless Steel items 11/7/17 @ 136k
Checked bottom of radiator – no leak 30/7/17 @ 137k
Replaced battery to chassis earth strap with 24" item 30/7/17 @ 137k
Replaced front and rear windscreen wipers Bosch -> Bosch 4/9/17 @ 137k
Tightened all boost pipes, rewired green / black cable on YCOD with bullets, sprayed MAF sensor with electrical contact cleaner, unhooked as many connectors I could see and sprayed with electrical contact cleaner, checked coil pack wiring is ok, coil pack connectors sprayed with electrical contact cleaner, checked cam cover earth was tight, checked elephants trunk which was unsplit, reseated GTEC 2, cleaned inside of EBC solenoid with contact cleaner, checked hard inlet pipe metal collar are in correct position, no boost splits for pipe just before inlet and just before inlet hard pipe, replaced 24” battery negative strap with 12” item as per OEM length & replaced 1 of the 2 fuel pump relays 26/9/17 @ 137k
Replaced Rocker Cover Gasket 6/10/17 @ 137k
Replaced Spark Plugs Bosch FR6KTC 6/10/17 @ 137k
Extra velcro on Richbrook drivers matt to stop it slipping 6/10/17 @ 137k
Replaced 5.0m interconnect to sub amp which was damaged with 2.5m interconnect and reduced speaker cable length for front Focals by around 1.0m 8/10/17 @ 137k
Replaced melted 30 amp fuse for heating circuit 19/10/17 @ 137k
Replaced other YCOD wire with spade connection 21/10/17 @ 137k
Rewired gearbox to chassis and battery to chassis including sanded off corrosion 21/10/17 @ 137k
Reseat and checked all fuses under bonnet and in fuse box 21/10/17 @ 137k
Replaced ECU with alternate with GTEC 2 and switched back to check for power loss – not ECU 21/10/17 @ 137k

Could it be that it's overboosting, so the ECU is intervening to cut boost? Can you replace the boost controller with standard setup to check?

Yes Good suggestion I’ve got that one on the list

Switch out boost controller to PRV
Switch out GTEC 2 to standard chip
Switch out other fuel pump relay
Run with no AFM connected
Soak AFM in contact cleaner
Check Fuel pipes in engine bay dry and tight
Breather hose deforming at high revs/pressure?
Compression test
Check wiring to starter motor / alternator
Check remaining earth straps

I've been thinking more about this and where I'm saying the Coupe won't do it on base boost and only on full boost, I get base boost by unplugging my electronic boost controller completely. So tomorrow I will run base boost using the EBC.

Run EBC at base boost (do not unplug)
Switch out boost controller to PRV
Switch out GTEC 2 to standard chip
Switch out other fuel pump relay
Run with no AFM connected
Switch out AFM
Soak AFM in contact cleaner
Check Fuel pipes in engine bay dry and tight
Breather hose deforming at high revs/pressure?
Compression test
Check wiring to starter motor / alternator
Check remaining earth straps

Today I ran base boost through the EBC and it generated the issue. I had to really ring it's neck to get it to do it and I'm not convinced I've tested under the same conditions with the EBC unplugged which I'll try tomorrow.

This is interim until I get get the energy up to sift through the boxes of Coupe parts in my loft to find the PRV.

Generated the issue at full revs again Gunzi?

MM

Yes today I drove it with EBC unplugged (base boost) and at 5.5-6k rpm it generated the fault.

It's interesting that on full boost it will do the fault at any rev range but at base boost it's only higher up the rev range.

This morning I switched the AFM to an alternative supplied by Bockers and will see what happens on the way to work tomorrow.

Alternative AFM still have the issue.

I’ve unplugged the AFM which generates an injector light (I never see this even with the issue).

Dont know much regarding amount of torque at that rev range, is this still creating the same fault as on your video i.e. rev counter dropping off etc.?

Can you get it to do this if you drive and alternate the accelerator pedal between on off on off etc (trying to recreate movement in the engine similar to it moving with high torque off boost??

If so, this could indicate a possible wiring issue related to movement of the engine, which would put the ball back in the court of a wiring issue

It is possible to have a stretched wire where the insulation looks ok but the wire within is broken and touching until moved!

The only thing that is odd is that its not intermittent but how you described only when on boost??

I was reading some of your past posts Chris with regard to the problematic Bosst controller.
Do you think it could be the controller?

Joe with the boost controller disconnected it will have the same issue but I have to really rev it, where as when it’s full boost it’ll create the issue almost anywhere in the Rev range.

H_R I will try to do this.

It doesn’t always do it, today I got 3 clean pulls through the Rev range using max boost with no issue then 5 mins later I went for a 4th go and it started to do it. Sometimes it’ll just do it every time I use full boost.

I know we are going over old ground,but what is you're dump valve situation? I remember Joe (cc) saying something about it to you.

It does not exist, I have run without a dump valve since 2008.

It’s on the list to try, but is £130 so trying other avenues first.

Another thought - have you checked the short small-bore pipe to the fuel pressure regulator?

If that is slightly split, it could cause the fuel pressure to drop - would be more noticeable at high boost

In the video you can see the rev counter needle dropping faster than the engine revs could possibly be dropping therefore it's not reading accurately and so it's almost certainly an electrical, not mechanical problem.

Probably a major power or ground issue that's affecting the ECU as the ECU controls the rev counter. ECU has been switched and problem is still present so my guess is a wiring, connector, relay or ground strap type problem somewhere or even ignition switch.

Or possibly some electrical component or sensor is failing under load and causing a short and power drain, although in theory that should blow a fuse. Maybe it could be a fault with the starter or alternator that causes a very quick but major short that drops power to the ECU without having the possibility to blow a fuse. Maybe even some weird fault with the battery itself, who knows.

A multi-meter probably wouldn't be fast enough to react to the power drop so you'd really need to hook up an oscilloscope to various power/ground lines and see if they flucuate when the problem appears.

I did read that an old battery can have a similar effect - but I am unsure how

i could get the battery with a volt meter. What readings would tell me if the battery needs replacing?

Will check the pipe to fuel regulator.

The ground checking is on the list for the weekend.

Ironically just ch3cked your startrek output and the battery was reporting 14.5v

So I presume that’s ok, but was that taken with the engine running?

When the power drops, does it feel like a hesitation (like lifted off to half throttle) or a full-blown cut-out (like you£ve lifted off the throttle completely)?

Also, do you get any clicking noises from around the passenger footwell?

I would definitely get hold of a known-good battery and try that - I’ve had a Coupe misbehave due to a failing battery - just because it will start the car doesn’t mean it’s still ok. Volts is one thing, but if it can’t supply the current, something has to give

What I did notice Chris is that the positive terminal on your battery was very corroded with what looked like sticky gunk etc.

When was the last time you disconnected it?

Earlier in the year when I switched the battery out but I didn't clean it up. Will add that to the list.

Complete cut out like I've lifted my foot off the throttle then smashed it back down again, expect I haven't.



I've not noticed but I have a stainless exhaust which is quite loud. It certainly doesn't click when I'm pootling around town using low revs.



I'll add it to the list!

Completed:
Tightened all boost pipes (nothing was loose)
Rewired green black cable on YCOD with bullets
Cleaned MAF sensor and sprayed with electrical contact cleaner
Unhooked as many connectors I could see and sprayed with electrical contact cleaner
Checked coil pack wiring, this was done a few years ago and it's all ok. Coil pack connectors sprayed with electrical contact cleaner.
Checked cam cover earth was tight
Checked elephants trunk which was unsplit
Reseated GTEC 2
Cleaned inside of EBC solenoid with contact cleaner
Checked hard inlet pipe metal collar whose metal collars are in correct position
No boost splits for pipe just before inlet and just before inlet hard pipe
Replaced 24” battery negative strap with 12” item as per OEM length
Replaced 1 of the 2 fuel pump relays
Replaced spark plugs with Bosch FR6KTC
Replaced 1 x coil pack which was split
Bypass other YCOD cable (connector now removed from car)
Check and reseat all fuses in engine bay and fuse box
Tested alternative ECU (thanks GrahamL)
Rewire earth connections and trim excessive insulation
Tested alternative AFM (thanks Bockers)
Run with no AFM connected (generated injector light)
Check wiring to direct fuel pump feed
Clean up positive terminal on battery
Clean rust off earth connections to replacement coil pack
Checked Fuel pipes in engine bay dry and tight - no leaks
Nipped up drivers front earth strap

Mechanical To Do:
Switch out boost controller to PRV
Breather hose deforming at high revs/pressure?
Compression test
Fit new dump valve
Check boost pipes beneath engine

Electrical to Do:
Check wiring to starter motor / alternator
Check remaining earth straps
Switch out GTEC 2 to standard chip
Switch out other fuel pump relay
Run with no AFM connected
Replace battery
Change fuel pump
Change other 4 coil packs
Replace battery / chassis earth strap with OEM
Rolling road diagnostics
Earth cable in boot drivers side rear light

Checking your remaining earth straps, and maybe swapping out the battery with a known good one sounds the next logical step Gunzi.

Keep on it-the answer is getting closer!

MM

Cheers MM, Im also going to try and source an original earth strap just to put it back to standard.

have you tried a different maf?

i would also be looking into 02 sensor condition also

maybe the knock sensor is detecting pre detonation so the ecu is cutting the power?
i had a focus that the power used to drop off for a few seconds then come back to life and it was the crank shaft sensor

i would go back to the standard chip with standard boost setting on a man boost controller and see if it still does it.

If the rev counter is dropping rapidly when the power cuts, its an electrical issue - nothing else could cause revs to drop so quickly

My money is now on a faulty chip (although voltage issues could cause a chip to behave badly, so definitely worth swapping the battery for a known good one)

I thought that was possible so fitted a new chip to the test ECU and the problem was still there so it seems it's not caused by the chip or ECU.

I still think it looks and sounds like the ECU is totally dropping ignition, injection, control of the rev counter, everything basically. Probably due to a bad power or ground connection, a wiring short, shorting battery or something like that but definitely electrical.

Yes I switched the MAF to no avail.

Crank sensor was changed in 2012.

Could wiring to O2 sensor have anything to do with it? Lambda was mentioned in the ECU scan.

Lambda sensor is ignored at full throttle, so I'd say no. Unless it's causing a short and you've replaced the lambda fuse with a fifty pence.

Hmmm - ok - I’m back to the battery as being suspect, but would the regulator/rectifier also cause some weird electrical behaviour?

Sounds like you are just bouncing off the rev limiter

Seriously, can you not get it on a rolling road and hook it up to some form of diagnostics? Hope you get it sorted soon.

Not touched the Lambda in my 10 year ownership, it’s quite possible it’s original.

I'd not thought about getting it on a rolling road for diagnostics. I'll add that to the list.

Next step is to check the remaining earths.

How could I check the health of the battery? Voltmeter? If so what value is good and what is bad?

I'd pay special attention to the earth on the back of the engine at the support bracket + the lower bolt on the bracket itself. Remove, clean and tighten at least.

As the problem is intermittent I don't think there's much you can do to check the battery with a multi-meter.

If it was some kind of weird, momentary internal short in the battery or alternator I think that would cause lights to flicker which presumably you haven't noticed. The way it appears to be affecting only the ECU suggests it's a more local ground/power/wiring problem, but I'd still try swapping out the battery even with one from another car just to rule it out.

Silly question but there's no wires damaged in and around the accelerator pedal or steering column...I had an old 205 gti that had cables everywhere wrapped round the column and as I turned the wheel it dropped power....it also on one occasion set fire to my carpet! Just wondered if something could be pinching somewhere on throttle as you said you had to hammer it a bit to get it to do it

Would just see if you can borrow a known good battery for a few days and see if that cures it- would be one less in the long list of possible things to check.

You could drain your wallet and your sanity by buying and replacing things you don't need to if your not careful Gunzi! (Not to mention draining your enthusiasm!).

Maybe-as this has everyone scratching heads - your funds would be well spent getting the car to one of the experts here, on a rolling road/ramp and paying an hour or two of their time to chase down the remaining options.

Could be money well spent and you get your coupe back to full health.

My money is on the earth straps/some wiring issue now I have seen your video. But I'm far from an expert with mechanics and others on here have vast depth of knowledge to guide you better then I.

I don't think your too far from getting this sorted and when you actually find the cause- it won't be too hard to fix.

Its just finding it. Keep going!

MM

I'm going to check to see if my Sykes Pickavant ACR shows ignition advance - if it does, it might be worth you borrowing it, as its possible to drive while it is working, allowing you to see up to four aspects of the ECU on one screen

It would need a passenger who knows what they are looking at, but it might give you a better idea about what's happening at the point of the power cut

Yes it does, so does a widget. But it only updates every so often, and the "spikes" that are seen may be too quick to be picked up and shared by the ECU (and after all, the ACR and widget are only displaying what the ECU cares to share with them). But with an ACR4 you can set up all 4 lines to display the same thing so that you might get to see the "spike"...?

And instead of a passenger, just secure the ACR4 somehow with a phone camera filming it...?

Yes, the ECU won't update at much more than once a second. The ECU processor is thick as a brick and it's really working hard to keep the engine turning; talking to anything else is really down the list on its agenda.

Today I've replaced my battery to chassis cable and what's left of the original gearbox to chassis cable with a replacement I belive from an Alfa 147 Diesel, which is significantly thicker, if about 8" longer between chassis and gearbox.

The test will be on Monday. Fingers crossed.

how did u get on?

I wanted to ask as well! Worried though in case its what tips him over the edge!

Well I’ve deliverately held off posting as my first full run gave a clean 2nd year and a tiny version of the issue at the top of 3rd. I’ve down 3 separate power runs since then with no issues.

I’m not going to say it’s fixed just yet but I feel like I’m damn close! Next job is clean up the negative terminal on the replacement cable and check the remaining earths.

Sounding good Gunzi!!

If you have found the key issue- what a search!

MM

Sounding hopeful Chris, fair play for sticking at it

Another day has passed and through the gears it's been perfect. I'm becoming happier as the days roll by!

Excellent, have you fitted a D/V yet

Don’t be silly

It’s on the list I just want to be really sure this problem has gone before moving onto the more minor items!

If the issue turns out to be earth-related then we will all be better off from your experiences.

Hats off to your persistence

Thanks Simon!

Not all rosey as today it did it again. Since replacing the battery earth cable there has been a huge improvement in that the frequency is now twice in 5 car journeys rather than multiple times every journey.

So I've sanded down the negative battery terminal which connects to the battery and will check / tighten the remaining earths this weekend. Then retest next week.

i have noticed when stripping mine theres an earth just behind both dash end covers and one by the bonnet release handle which was rusty on mine.
just thought i would throw it out there!

Thank you Liam, will add these to be inspected to the list!

I've done about 12 journeys since the sanding and not had the issue at all.

It occurred to me that the original earth cable has metal connection to the battery terminal where as the replacement has a gold type coating on it. The Alfa diesel cable had a white film over it when I originally installed it, after sanding now back to the original metal.

This whole thing could be down to the quality of the connection at the actual battery terminal.

Will report back over Christmas, but so far, so good!

Excellent news Gunzi! What a mammoth hunt to find the cause!

Get a DV fitted and hopefully you can start to enjoy her properly again!

MM

Cheers MM, it’s been quite a challenge!

Getting a DV is on the list, it’s a pain in traffic as it stutters and is not smooth to pull away, but it sounds excellent on gear changes even with a tiny whiff of boost.

I wonder what Joe CC thinks...?!

Fingers crossed that's it sorted, you're a stubborn git model of patience and tenacity

Where you have rubbed down the contacts, apply some vaseline. Sounds counterintuitive, but it'll form a layer only thick enough to keep the air from corroding the contact while still allowing good contact.

Will do, cheers Neil.

It’s been a hell of a trial but I’m happy to have her back to normal Simon (still keeping fingers crossed!)

I'm marking this one as SOLVED!

The original battery negative earth cable goes to chassis and then onto gearbox. My original cable was frayed between chassis and battery so I snapped it off leaving the original cable between chassis and replaced the chassis to battery portion with a cable from ebay.

It turns out the ebay cable wasn't sufficient when on full boost, and cut the engine power. When I replaced the earth terminal to chassis to gearbox cable with one from an Alfa 147 JTD and cleaned up all connections the issue went away.

Gunzi-just answered your post about new stalling issues?? confussed (does not take long)

Is she fixed-or stalling and not running now?

Hope its fixed!!!!!

MM

Hi MM,

This stalling is definitely a separate issue to this one. I suspect an air leak as one of the things I did when looking for this issue was tighten all boost pipes and may have been over zealous and one has now sllit!

That's v bad luck Gunzi,

I hope its a quick find and you can get a new hose as soon as possible if that's the cause. Must have developed a big tear quickly for it to go so bad so quickly-no chance pipe is off completely somewhere?

She is fighting you at the moment but you will get there.

MM

edit reason...spelling!