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#1623742 - 08/08/2018 17:50 Alfa GT JTDM 1.9 Power Loss
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
The Alfa's up to about 170k now and has just lost most of its power. It starts and idles but stutters under load and won't rev happily beyond 2000 rpm.

The engine light isn't on although I haven't scanned for fault codes yet. It has felt reluctant to pick up boost initially over recent months but that goes after a couple of minutes usually.

There are no unusual noises, but I can't hear the turbo.

A quick web search seems to turn up turbo, EGR stuck open, I I thought fuel pump possibly but that doesn't seem to come up.

Sorry to be asking on the wrong forum but I know a few people on here are running the 1.9 JTD lump in various cars. Does anyone have any ideas / similar experiences with the JTD?



On a more relevant topic the Coupe has come on well recently. I decided to change the alternator and that turned into a project that involved new exhaust manifold, new cambelt, new rear exhaust, some painting of things like heat shields, and a bit of a go at the Eiffel towers at the front, but it is all back together ready to fail an MOT so hopefully it won't be long before I can come along to a meet. click to enlarge

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#1623743 - 08/08/2018 18:04 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
DaveG Offline
Club member 311
Forum is my life

Registered: 16/12/2005
Posts: 6953
Loc: Lightwater, Surrey, UK
Hey Peter, we've not seen you around for a while?

Check the boost hoses, sounds similar to a problem on wifey's old Volvo TD, think that was also accompanied by copious amounts of black smoke (which you didn't mention) but worth a look, they always seem to split out of view...

As for the Coupe, well done, doing lots more than is strictly necessary is what I'm doing to the Porto 20vt (rear brakes failed MOT, now turning into a mini rear suspension overhaul, as well as the brakes)
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1996 Portofino 20vt & 2000 Pearl White Plus
1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake

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#1623745 - 08/08/2018 19:16 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
Nigel Offline
Club member 123
Forum veteran

Registered: 16/12/2005
Posts: 16932
Loc: Staffordshire
My GT is now at 247,000 miles and still going very strong

Get the codes read - loss of power could be down to lots of things

Boost leak will be accompanied by a hissing noise

It could be the MAF sensor, EGR valve, swirl flaps, injectors - lots of stuff
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#1623750 - 08/08/2018 22:00 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Hi Dave
Thanks for replying - I just had a dig around the front and couldn't see anything. Then started the car and it seemed like it had been, very slow pick up until I revved it a bit harder and it started to pick up better but with a bit of a stutter when I drove it at times, so I don't know if my rummaging around the hoses has changed things.

Good that your Porto is going from strength to strength.

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#1623786 - 10/08/2018 08:51 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Thanks Nigel 247,000 gives me hope
I'll try ECU scan on it when I get a chance

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#1623822 - 11/08/2018 16:11 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
whatmoretyres Offline
Forum is my job

Registered: 23/08/2006
Posts: 3694
Loc: burning oil in the alfa
Easy one to check is the lower turbo hose, it rubs on the bracket and splits - Autolusso do an uprated one. When I had EGR sticking it threw the engine light straight away.
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#1623958 - 14/08/2018 06:34 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Thanks for the advice - I'll have a closer look at the lower turbo hose. Whatever it is seemed to make it run on three cylinders for a while. It is some time since I've looked at the EGR. I've also been looking at swirl flaps on the Internet.

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#1623988 - 14/08/2018 19:57 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
coupedummy Offline
Club member 1341
Je suis un Coupé

Registered: 25/09/2006
Posts: 8939
Loc: west bromwich
I had almost certainly the same issues on our 147 jtdm. Checked hoses, replaced afm,blanked egr still same issue without any codes.
Would be looking at turbo directly possibly.

In the end it killed itself with the oil cooler bursting dumping all its oil..
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#1624053 - 17/08/2018 09:16 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Thanks Coupedummy. I've started on the swirl flap box set on Alfaowner. It seems they break off and then go through the engine and turbo from around 100,000 miles with varying levels of carnage. It would explain the way one cylinder was missing but then came back when it happened, but I didn't get any knocking from the engine at the time.

Nigel - did you do anything to your swirl flaps?

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#1624062 - 17/08/2018 15:04 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
Nigel Offline
Club member 123
Forum veteran

Registered: 16/12/2005
Posts: 16932
Loc: Staffordshire
Originally Posted By skinflint
Nigel - did you do anything to your swirl flaps?


I have no idea if my swirl flaps are still present - I've never looked

I would expect that if I could be bothered to look, I'd find that they are all gone, especially at the mileage its done
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#1624156 - 21/08/2018 10:33 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Thanks Nigel - that's reassuring.
Plan of action is:
Code read - may point to injector issues?
Check lower turbo hose
Take off / clean EGR
Clean MAF
Take off inlet manifold to inspect swirl flaps

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#1624251 - 23/08/2018 13:00 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
ScouseCoupe Offline
Club member 1433
Enjoying the ride

Registered: 10/04/2015
Posts: 487
Loc: China & Ayrshire
Originally Posted By skinflint
Thanks Nigel - that's reassuring.
Plan of action is:
Code read - may point to injector issues?
Check lower turbo hose
Take off / clean EGR
Clean MAF
Take off inlet manifold to inspect swirl flaps


If you change the EGR, you will find the part is fraction of the price if you purchase a GM Vectra C part as opposed to the Fiat/Alfa price. The EGR is the same in the Alfa, as to a VX and Saab.
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1999 Speed Red 20VT ( Standard & Stock )

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#1624300 - 24/08/2018 18:02 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Thanks for that info - The EGR came up as the only error, but didn't come back when I cleared it.
click to enlarge

There also seems to be a consistent correction for injectors 3 and 1 - although I don't know if the values shown are all that significant.
click to enlarge

The lower hose was rubbed as suggested by the battery earth lead but not through yet.

EGR makes a faint click (is that normal?) when I activate it from MultiECUScan and has just a dusting of dry soot which makes me think that my swirl flaps probably aren't all gummed up.

Turbo can now be heard spinning up.

Some other thoughts are that as the car had been laid up for a few days maybe the battery was weak, or maybe some kind of fuel contamination blocked the injectors or affected the fuel pressure.

Any thoughts?

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#1624309 - 24/08/2018 23:17 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
Nigel Offline
Club member 123
Forum veteran

Registered: 16/12/2005
Posts: 16932
Loc: Staffordshire
Have it Terracleaned - makes a world of difference - added about 4mpg to mine
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#1624317 - 25/08/2018 07:49 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
barnacle Offline
Club Member 18 - Membership Secretary
Forum Demigod

Registered: 17/12/2005
Posts: 31878
Loc: Hemel in the Hempstead
If I saw something similar to those injector corrections on a petrol engine with a plenum, I'd assume that injector 3 was getting more flow than it should and the other three are being reduced to compensate (1.74 + 0.54 + 0.74 = 3.02) but I'm not at all sure that's what the correction actually means (and whether that would work the same way on a diesel).
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#1624335 - 25/08/2018 16:07 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
I had a look online and couldn't establish anything to suggest either way. My thought was that no.3 is pissing rather than spraying but I don't know how the car can sense flow to each cylinder?

I put some cheap injector cleaner in and ran it for 20 miles. The numbers are now about 20% closer.

They get closer still at higher revs..
click to enlarge This was from idle - the closer part is around 2000, they diverge at 2500 rpm.

I also got a new battery for it as the car has done mad things in the past with a weak battery.

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#1624351 - 26/08/2018 07:27 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
barnacle Offline
Club Member 18 - Membership Secretary
Forum Demigod

Registered: 17/12/2005
Posts: 31878
Loc: Hemel in the Hempstead
That was my thought; you can't tell an individual flow on most petrol engines because in general they flow into a plenum chamber where anything that doesn't make it into a cylinder is available for the next cylinder and it averages out.

And even though a diesel injects directly, so each flow is independent, I don't believe that the lambda sensor can react quickly enough to isolate the effect of each pulse.

But your graph shows a change, and it doesn't look like a mapped change but more as a response to a changing engine condition, so perhaps they can?

[After some research]
I can't find anything conclusive, but some interesting hints on scientific papers behind paywalls (and which therefore I have not read!) suggest that:

a) the time constant of a normal lambda sensor is around 50-100ms (a four cylinder engine generates an exhaust pulse every 20ms at 3000rpm)

b) that if the sensor is mounted very close to the exhaust valves, it is possible to isolate and measure individual pulses

But I found nothing about the effect of the turbo getting in the way of the exhaust pulses, so I still don't know exactly what's being measured...
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Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

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#1624373 - 26/08/2018 20:32 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
One possibility...
There's an article here that suggests the JTDM engine injects a small pulse of fuel at the start of the cycle at low revs but stops doing this at high revs.
Alfa Workshop JTD Engine Overview

Another possibility...
I think the conclusion to your points is that the lambda can provide some feedback to individual firings at low revs but perhaps not at higher revs, so maybe it doesn't correct something it can't measure?

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#1624418 - 27/08/2018 22:02 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
barnacle Offline
Club Member 18 - Membership Secretary
Forum Demigod

Registered: 17/12/2005
Posts: 31878
Loc: Hemel in the Hempstead
That's possible.

On a semi-related note, I'm trying to find why my 105 Eco 1600 diesel intermittently has no power at very low revs... Joe and I had a bit of a fettle this weekend and came only to the conclusion that the turbo boost control is both perverse and inverted (it uses the vacuum from the brake pump to hold the wastegate closed), and that the ecu isn't telling the wastegate to open...
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Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

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#1624458 - 28/08/2018 19:30 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Is that something you can trace using MultuECUScan and the graph function or is it so intermittent that it just won't happen from one minute to the next?

I have a possible cause for mine. The water pump is weeping so could have been spitting coolant at the cam position sensor. It would explain why the problem went away when the car was left (i.e. everything dried out)

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#1624459 - 28/08/2018 19:34 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
barnacle Offline
Club Member 18 - Membership Secretary
Forum Demigod

Registered: 17/12/2005
Posts: 31878
Loc: Hemel in the Hempstead
Sadly, no. It comes and goes, and the problem is you never know whether you're going to scoot out of a junction, or put put put...
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Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

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#1624460 - 28/08/2018 19:43 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
skinflint Offline
I need some sleep

Registered: 07/02/2007
Posts: 3176
Loc: West Berks
Some people suggest the EGR for this kind of issue too. On the 1.9 I guess you could take the solenoid off the EGR body by undoing the 4 Torx bolts and cable tying it to something to achieve this.

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#1624467 - 28/08/2018 20:33 Re: Alfa GT JTDM 1.9 Power Loss [Re: skinflint]
coupedummy Offline
Club member 1341
Je suis un Coupé

Registered: 25/09/2006
Posts: 8939
Loc: west bromwich
You can blank the Egr. A light will most likely pop up on the 16v(doesnt on the 8b) but at least you can test. When removed you would also likely see a mass of carbon build up which is worth removing.


Edited by coupedummy (28/08/2018 20:33)
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