Cold start stalling and hesitation

I really need some advice here, I'm pulling my hair out and I'm about to give my car a dam good Basil Fawlty type thrashing with a tree branch!
It's a year 2000 20VT Plus with 133k on the clock which I have owned for 14 years. It's been off the road for the last 8 months as I have been rebuilding the back end (subframe, fuel tank and exhaust off and cutting out rust / welding (the battery was removed)). She was running fine before. It went through it's MOT with just two small advisories, but just passing the emissions test.
It cold starts fine, but then after about 20 seconds it stutters and stalls. I can keep the engine running using the accelerator pedal. Once warm it idles fine, but will hesitate when driving at over about 3000 rpm to the point that it does not accelerate when I stand on the accelerator and will missfire. It will happliy cruise at motorway speeds and can gently accelerate. I suspect the engine is running rich from the petrol smell out of the exhaust!
I have replaced the following with new Bosch parts: fuel pump, fuel filter, fuel pressure regulator, MAF. I have also replaced all 5 injectors.
The coil packs all measure 0.4 ohm and all of the spark plugs are the same colour; light green tint (which I think means running hot) with some black soot at the base.
The throttle position sensor is giving me 0.4 V at idle position and 4.6 V fully open, the air and engine temp sensors are giving good readouts.
The idle control valve has been cleaned 3 times now and I have an actuator test routine so I can see the gate opening and closing on command from the ECU.
The lambda probe is giving almost 1 V when removed and heated with a blow torch, and I have 12 V at the probe for the heater.
I have checked for vacuum leaks, both visually and with propane and I can't see a leak. I haven't checkd the charge pipe to the intercooler, or the intercooler yet.
The timing variator solenoid relay is good and I can feel and hear the click on the varator when revving the engine.
Even the atmospheric pressure sensor is giving good readings (1020 just now).
The ECU is reporting no faults apart from after a stall, when I get autoadaption parameters FRA - outside maximum plausable limit and Sensor Integration FR - Above maximum limit, but I assume these are due to the stall.
I have a new Bosch lambda probe comming tomorrow.
Can anyone help please? My next step is the branch...

I had a similar issue on a Moto Guzzi fuel injected bike about 12 years ago which I eventually traced back to the crank sensor but only once it had failed altogether and the bike just refused to start.

I recently asked on here about a warm start issue on my 20VT and Countrycruising said most likely the crank sensor - I had ruled this out because of my experience with the Guzzi. However having now fitted a new crank sensor it does seem to of solved the problem, fingers crossed. It seems as they age they play up in different ways.

On my fiat ducato van which is clearly not the same beast

I had to change the cat as it was clogging up and not getting rid of fast enough

Granted I also had to get all new injectors and countless other things before it’s back to normal and not running like a
Bag of spanners again

Thanks Clanger.
Was the crank sensor a specialist job to replace? I think it's the sensor behind the exhaust side cam shaft cog.

There are a couple of threads on here detailing it but essentially you can get at it from above or below. Either way your working blind.

I removed the small bracket on the bulkhead held on with 2 bolts that holds the air pressure sensor and a fuel vapour valve and pulled it forward. This allows you to put your arm behind it and reach down the back of the engine, just below the started motor to get to the sensor without scratching your arm to bits. Because of where it is, it sounds difficult but its actually straight forward once you have found it - one cap head bolt, 5 mm allen and then a bit of pulling to remove. The new one equally needs a good firm push back in to seat it in the hole properly. The bolt is a bit fiddly to replace, I used my fingers to get it started (oh er) but as someone suggested you could tape it to the allen key.

Ah, do you mean the rpm sensor?
I was thinking that you meant the timing sensor located behind the exhaust camshaft pully, which would be a nightmare to change I think (cambelt change procedure) and not for me on the drive!
Thanks for your help, I really appreciate it!

The new lambda probe made no difference so I've ordered a new crankshaft sensor. Should be with me Monday or Tuesday.
I'll let you know how I get on...

Could still be a coil pack. I've had three of the Bosch originals fail in the last couple of years, the third one with similar (though not identical) symptoms to yours. After being Sorned for winter the car started and idled fine and sailed through MOT on emissions but hesitated under hard acceleration. I temporarily connected a boost gauge to check all was well there and changed the old-ish fuel filter but after that as two of the coil packs had failed recently I suspected another one and tried substituting a new one for each cylinder in turn. After much testing and head scratching the new coil pack seemed to improve but not cure the misfire when substituted for each of two packs - one of the original Bosch and one of the replacements, which was a ebay cheapie. All this suggested: A. Both were failing under load. B. Cheap coil packs might be a false economy. C. The two remaining good Bosch coil packs were still giving great service after over 20 years but couldn't be expected to last much longer.
So I took a deep breath and ordered and fitted five new Bosch coil packs and now the car is running beautifully again.
You mentioned the plugs all looking the same and it was the same for me with failing coil packs. No fault codes in Multiscan either.

Thanks AndyL.
I want to put my fingers in my ears when I hear coil packs, but if the crankshaft sensor doesn't cure the problem that will be the next thing on the list.
I think that 3 of the 5 are originals, and I fitted 2 second hand ones about 10 years ago! So I'll get 5 new ones. At about £50 each it will be a sore one but I can't give up now!
Thanks again.

Hmm,

Just to add food for thought - after my 20vt was tuned by Mr Flea (I would never have another coupe without having this done) I had problems with rough running and struggling performance. It came down to a dying fuel injector (thanks to Mr BBR who kindly scaned my car as I am a technophobe).

Symptons were similar to yours. But a scan did show up the code to reveal the issue. But I had a good 45 minute drive over to his first, so car was well warmed up. I just wonder if a scan after you have warmed through your coupe may throw this up.

I picked up 2 known working injectors so have one spare now-but should get some more. And - problem resolved!

Anyhow - just food for thought., Andys comments make me think I should get a coil pack in or two just for spares..

Parts for coupes are getting a bit silly to find, and more expensive...its a bit of a rocky road if your relying on them for day to day driving now-as its hard to locate some items quickly!

Best wishes,

MM

Thanks for the comments MM.
I actually fitted 5 new injectors and they made no difference

I've just fitted a new crankshaft sensor and guess what, no difference

So, 5 new Bosch injectors comming Thursday! The spark plugs only have a few hunderd miles on them so they have to be OK...

I'll let you know how I get on. At least I have a good set of spare sensors . Always look on the bring side of life.

I replaced my crank sensor from below, once you find where it is it was a relatively simple job that probably took less time than getting the car in the air to get under it!

MIB,

If you have done all the injectors, and you are going to do all the coils - just go for a new set of spark plugs - at least you rule them out as well and they will be the lowest cost answer. And check all the earthing points.

That's a serious commitment your making to resolve this issue- hopefully it will be resolved very quickly.

MM

The saga continues
Today I replaced all 5 coil packs and spark plugs and I'm no further forward.
I can't understand how the car will start first time and idle quite normally for 15 seconds or so and then stutter and stall. On the road (just up to 30 mph) I get no acceleration and a missfire.
Anybody got any ideas? I've spent a small fortune on new, genuine parts with zero progress. Am I missing something totally obvious?

Do you have access to a known working MAF? They can cause all kinds of issues but rarely get replaced due to the cost. Don’t try an after market part as they are total crap.

Thanks french_coupe, but I have already replaced the MAF with a new, genuine Bosch part.

I have replaced (with new Bosch parts):
5 Injectors
5 Spark plugs
Fuel pressure regulator
Fuel pump
Fuel filter
Crank sensor
Lambda sensor
MAF
I've cleaned the ICV several times and confirmed that it operates. The throttle position sensor is giving a good varying voltage when pressing the pedal and is about 0.4v at idle.

Have you checked out the air filter/box?

Yes, it's all clear and the filter looks good.

Might be a vacuum leak, but I'd get it on live diagnostics to check sensor values in real time and see what's happening with lambda among other things. Also fit a boost gauge if you don't have one, could be very revealing to see what vacuum and boost you're getting.

My car was stalling on idle like yours from cold and often when warm as well and was down to the ICV. Not sure about the other hesitation, but the ICV does keep the "base" revs.

I cleaned my ICV. Original Bosch jobbie as I'd never changed it (or cleaned it!) in 14 years of ownership. Idled much better for a while, but got a judder when taking off some times, like not giving enough revs and nearly stalling. Then it started nearly stalling again when engine was warm.

I'd bought a replacement ICV (Intermotor) so replaced it and fine ever since. Revs when engine cold a little higher than before (probably how it should have been), revs rock steady at all other times and judder gone. So must of been an aged ICV not responding well enough?

If there are no fault codes and with everything that you have replaced I would think that it must be a split hose with either a vacuum leak / air getting in somewhere it shouldn’t.
As you know there is a lot of pipe work small and large. Even a small split can cause big problems.

Just another idea to chase.

I dimly remember someone somewhere having similar issues. And the source of all of it was water in the fuel!

If you can't find a split pipe/spilt doughnuts on the inlet manifold - how old's your fuel? Is our car kept outside/had any change of the fuel becoming corrupted?

Also - just check all your main earthing points are still earthing well..

Regards

Thanks for all of your comments!

1st_things_1st : I've cleaned the ICV and the software that I use (DnEcuDiag) has an actuator test routine for the ICV. With the ICV taken off the throttle body I can see the valve fully open and fully close on command.

The ICV does sit slightly open when the engine is off. Does anyone know if this is correct? I assume it is, as some kind a fail safe.

french_coupe : I'm thinking more and more that this must be a vacuum leak. I have looked everywhere and I can't see one. I have also tried propane gas (and carb cleaner) to see if I can get a brief increase in revs if the gas / fluid finds a split, but nothing.

Master_Mariner : The car had been sitting for 8 months with some fuel in the tank, but it has since been filled and I have use about 3/4 of that tank.

I have just done a fuel flow test to try to be sure that there isn't anything restricting the flow of fuel to the rail. I disconnected the fuel supply tube at the rail and popped it into a large glass jar. With the fuel pump relay removed (and the lambda probe disconnected as they run off the same relay) I pushed a wire into each relay socket contact with a switch at the other end of the wire placed in the engine bay. I then ran the pump for 5 seconds and the jar filled with 1/3 litre of fuel (~240 l/hr). I think that the minimum flow rate is 110 l/hr, so I'm happy that the fuel supply is good.
I also stood all 5 injectors, still attached, in jam jars and cranked the engine. All 5 group fired at first and when cranking they sprayed the same pattern and the same amount of fuel into each jar.

So my next step is to find a local garage that can do a vacuum / smoke test on the intake. I'll get there eventually...

Pull the pipe off the turbo output and block it, then start the engine and it'll suck all the air out of the intake pipes and collapse them, then stall. You can then hear where the air is getting sucked in if there's a leak, as the pipes take shape again.

I'd also fit a boost gauge if you don't have one, will be very useful to know actual vacuum level and what the boost is doing when it misfires. You can even just plumb it in temporarily with hose tee'd in at the FPR, pipe in the driver's window and gauge taped to the dash.

Just collected the car from a local garage where they had a poke about.

They have measured the fuel pressure as 2.5 Bar on idle and 3.0 Bar throttle open, which I believe is OK.

Idle vacuum as 59 kPa / 17 inHg which dropped at 0 when the throttle was opened. I think that this is OK too.

Keeping the car idling on cold start is difficult and there is no power when tying to accelerate in any gear

I'm completely out of ideas now (and several hunderd pounds worse off).
Unless anyone has any other ideas, can anyone tell me the nearest trusted specialist to Newbury, West Berkshire?

I'm not allowed sharp objects and my wife has removed my showlaces, so I need help

Joe at http://www.fiatcoupespecialist.co.uk/ is an hour and half from you (well when he returns from Turin of course in the next couple of days)
Flea at http://www.fcperformance.co.uk is at Castle Coombe these days I think and that is even closer to you

There will be more I am sure

Thanks BBR! I think that I will give Flea a call.

Could a faulty knock sensor be giving me these problems? I think that they can be tested using a voltmeter to check for a voltage while tapping them.

Apart from the cam sensor, I think that they are the only sensors that I haven't replaced!

Another Coupe specialist is John Cartlidge aka Midlands Car Servicing, in Loughborough. He knows these cars inside out.

Yeah of course JBT, but he would be over 2 hours away from MIB wink
I didn't list every specialist for that reason
- if I had done Autosportivo would have been someone closer than JBT as well

barnacle may be able to add some of his vast knowledge here - but I think the ECU only uses sensor data within certain time frames and certain rev limits due to its criminally insufficient capabilities so it could be the ECU having got its knickers in a twist and only becoming apparent when it is being used.

I am no expert on this but gaining fault codes at different points in the start up may help.

I also had an issue with tick over and it ended up being that I had connected two sensors the wrong way round - on the 16v the ICV and cam position sensor have the exact same connector and can reach each other - DOH

*barnacle*

Thanks guys!

I have booked in to see Flea next Thursday (4th July).

Hopefully it's something silly and cheap. I'll be both happy and p'ed off at the same time if it is!!

I haven't enjoyed my Coupe since last September, so I can't wait to get it sorted.

I've been watching, but it's been a few years since I had to fettle a 20vt so I don't have any immediate suggestions. If anything comes up, of course... My best guess, given your list of changed parts, is an air leak post the MAF, but a guess is all it is.

Neil

Thanks Neil,
An unmetered air leak was my thoughts also, but I couldn't find any using gas or carb cleaner.
I aksed my local garage to check for vacuum leaks and they couldn't find any either They measured vacuum as 17 in Hg.

Your in safe hands with Mr Flea!

And should he breath on your coupe and tune it - you won't be disappointed!

MM

Check the earth from battery to chassis, check earth under rear lights nearside and also check the plate under inlet plenum just above chod .
Check all nuts are tight .
Might just be something simple like this .
Fingers crossed

So...
I visited Mr Flea yesterday and he diagnosed the problem as rubbish, aftermarket, non-genuine, far Eastern fuel injectors!
My mistake for buying 'good value' components! I would have saved hundreds of pounds in parts (as I was going through a process of elimination) if I had just bought new genuine or even used Bosch injectors.
Fortunatley for him, the E-bay seller has agreed to a full refund (after a small messaging bun fight). These injectors were marked with the Bosch registered trademark and so were legally counterfeit!
Lesson learned; move on and enjoy the ride I'm now getting thanks to FC Performance!

Hmm, interesting. I bought a set of Bosch injectors a while ago, and they should have a special security code and "silver" sticker or hologram plus "data matrix" code (like a QR code) on a strip of paper sealing the box that directs you to www.protect.bosch.com where you can check if you have a genuine product.