2.0 TDI DSG - stalling at idle

[yossarian]

My 3 month old Golf 2.0 TDI DSG has developed a slightly alarming fault: occasionally, the engine will stall/cut-out at idle speed.

The fault only occurs under the following conditions:

- Transmission in D mode
- The engine is cold, probably less than 3 minutes run time
- The engine has been sitting at idle for several minutes (eg. waiting at train level crossing)
- The engine starts running very roughly, and the idle speed starts hunting around in a +/-100RPM band
- The engine re-starts easily after the cut-out

I have noticed that the engine always idles quite roughly when it's cold, but evens out once it has warmed up. It has that lumpy feel like a V8 with a racy camshaft.

The engine has stalled 4 times in the three months since new (a bit over 3000km of driving). As far as I'm concerned, this is 4 times too many for a brand new car!

I've had the dealership service department investigate the problem twice now, but they have not been able to replicate the fault in the workshop, and the ECU has no stored trouble codes.

Any ideas what could be causing this?

[brackie]

If the computer can't find the fault it's gonna stump the "techies". I certainly don't have enough knowledge of the ECU controlled modern diesels but if it were an "old technology" diesel I would be suspecting bad fuel.

[yossarian]

I would suspect that fuel has something to do with it. It's a diesel, so it should only really stop if it's not getting enough fuel - no spark or throttle to worry about.

I assume (or at least hope very strongly) that the service staff would have checked something as obvious as a dirty fuel filter. I'm guessing it's some sensor playing up just enough to confuse the ECU into not giving enough fuel, but not enough to register as an actual fault.

[gldgti]

I would suspect that fuel has something to do with it. It's a diesel, so it should only really stop if it's not getting enough fuel - no spark or throttle to worry about.

I assume (or at least hope very strongly) that the service staff would have checked something as obvious as a dirty fuel filter. I'm guessing it's some sensor playing up just enough to confuse the ECU into not giving enough fuel, but not enough to register as an actual fault.

as my dear ol dad always says "To assume is to make an ASS out of U and ME". - no offense, just wanted to say that.

anyway, they might not have checked it, its reasonable to expect that guys at dealer service shops don't do the simple things because they may well spend all the time trying to find out why the ECU isn't telling them whats wrong (i wonder what its like to have a car that does that....)

i agree with brackie, HOWEVER - lack of fuel is almost always noticed when you use a lot of it - full power, under load, thats kind of thing. a diesel with the most horribly blocked crudded up fuel filter will almost always idle without issue.

a problem that springs to mind to me, especially noticable at idle, could be AIR. air in the lines, at low rpm, may well cause the car run rough/low rpm and maybe stop. it could be that the fuel lines somewhere are letting in a little air until they warm up and become a little more supple.

hope this helps!

[Altered Sprinter]

My 3 month old Golf 2.0 TDI DSG has developed a slightly alarming fault: occasionally, the engine will stall/cut-out at idle speed.


Any ideas what could be causing this?

Simple question which area do you live in!
Which fuel are you using
NSW Vic has been using intermix fuel via transmix over seas prior to delivery
are you using Older diesel formulations with a 50pp/m or the new fuel from Mobil Shell and BP which is 10/ppm
Simple test for fuel put some in a small bottle and let it settle it should be clear with a low turps smell no water at the top or rainbow effect from contaminated fuel sources.
Your vehicle is set for euro 4 fuels via the EGR system , it's very touchy
a Teck won't pick up on this via a DBR test on the computor assist module as the engine has reached a higher temp already apart from that most have not susficent training to determine basic issues like fuel related problems untill a failure is found, fuel filters block or become waxy and include rust and water particles that effect the spray patten from the EGR system carbon blocks the front of the valves and the rear of the inlet port, so the valvue does not compleaty close, loss of rpm results
bore walls become glazed and crowns on the pistons are burnt.
It takes a very short time for oil sludge to build at the bottom of the pit
Do not over rev the engine when cold you will damage the system
Richard

[yossarian]

Well, it just did it again today - that makes 5 times now.

Interestingly, it stalled as I changed from park into reverse. I wonder if it's actually a fault in the transmission (or more likely the clutch) that's causing the problem? If the solenoid that actuates the clutch is malfunctioning such the the clutch is not fully disengaged, that would load up the engine and either cause it to run roughly or stall at idle. Evidently, the problem only occurs when the transmission oil is cold, too.

[Altered Sprinter]

Faulty pawl valve.... combined transmission senors, low ATF fluid
take to dealer for diagnostic testing on DRB testing
Question have you got bare bones on board computer assist! or do you have computer assist? that shows possible code fault
Stalling idle speed in reverse from start at cold start is a possible indicator to fuel starvation, EGR jets may be part blocked, high pressure pump may be out of sink with fuel pump distributor-fuel cooler or both, fuel rails may have contamination, causing full pressure flow, to be in part restricted ?????
Your vehicle is too new to be developing a mechanical wear issue, either you have defective fuel, or a sensor problem.
Richard