Engine Stuttering Hesitation at Constant Speed (Tdi)

Foghorn

Member
Chaps

An issue cropped up that has got progessively worse. Originally I noticed a sort of stutter in the engine when I was driving on the motorway at constant speed. No difference to acceleration as it pulled like a train.

As the days have gone on the stutter/hesitation has been noticeable at town speeds and sometimes during light acceleration under 30mph. Seems to come on when the engine has warmed up. Starting and hard acceleration and there is no apparent issue. Rock solid tick over.

I did think fuel filter/dodgy fuel but its inconsistent and some qucik searches have led to me to suspect other things. Car is on 150k, faultless up to this point, fuel filter changed at 80k (but looked brand new), original glow plugs etc.

There's no sign (yet) it will cut out on me but just be somewhat erratic however I've got a couple of long distance trips coming up.

Any suggestions as the best place to start?
 
You have changed a fuel filter in 70k miles?
I change mine every service which tbf is a bit oTT but keeps the injectors clean

Sent from my SM-G935F using Tapatalk
 
as youv done 70k since last changed ....change the fuel filter first and then see how she goes apart from that injector loom is the only other common fault to cause a missfire
 
I thought the service schedule on the fuel filter is every 80k miles? It was a complete PITA last time and given what came off I'm doubting the filter will be clogged, however I will give it a change.

I've heard things like injector wiring loom, MAF clogged or EGR clogged that could cause the same symptoms. How can I diagnose these, particularly the wiring loom?
 
I took my injector loom out cleaned it and put it back been fine since so free fix there.

Sent from my SM-J510FN using Tapatalk
 
Some further info. Car was fine today but as the engine starts to get warm then it starts to stutter. I'm thinking less a fuel filter issue as its inconsistent and more the wiring loom where heat might break the connection briefly?
 
Hi 'foghorn',

I have/had exact symptoms, Although it didn't matter wether engine was warm.

I decidied after driving nearly 10k miles like this enough was enough, I was going to tackle fuel first so I changed filter today and you wouldn't believe the black gunk on underside of the lid and the filter well you can guess. Cleaned it all up popped new filter in snapped small screw �� never mind. Took a while for engine to fire (waiting for fuel) drove to shell, filled up with V power diesel and after 100miles on i have full boost no shuddering at all.

I would consider trying this first, only £20 for new filter and around 1hours fitting ����

Pictures to show you the amount of dirt in fuel filter:
image.jpg image.jpg
 
Last edited:
Have you managed to change your fuel filter 'foghorn'?

Would be great to hear from you and see if this has solved the issue with your A2

Ross
 
I thought the service schedule on the fuel filter is every 80k miles? It was a complete PITA last time and given what came off I'm doubting the filter will be clogged, however I will give it a change.

I've heard things like injector wiring loom, MAF clogged or EGR clogged that could cause the same symptoms. How can I diagnose these, particularly the wiring loom?

Regarding the MAF - remove the connector to the MAF, engine will then run an a default MAF map, if it runs better with the MAF disconnected then it would be worth cleaning / changing it
Regarding EGR, assuming the AMF engine, remove and blank the vacuum pipe to the EGR, this will effectively remove the EGR from working, engine will likely run better without the EGR and will certainly be cleaner in the inlet manifold, some state it will take longer to warm up, but I have not seen anything noticeable other than a cleaner running engine and no mooing noise.

As for the wiring loom, that is some what more difficult, you could remove and clean it, but it is only about £60 new so having removed it I would replace it with new, even if it does not remove the problem at least you know that the loom is OK and it will have removed a common failure mode for the future.
Cheers,
 
Hi 'foghorn',

I have/had exact symptoms, Although it didn't matter wether engine was warm.

I decidied after driving nearly 10k miles like this enough was enough, I was going to tackle fuel first so I changed filter today and you wouldn't believe the black gunk on underside of the lid and the filter well you can guess. Cleaned it all up popped new filter in snapped small screw �� never mind. Took a while for engine to fire (waiting for fuel) drove to shell, filled up with V power diesel and after 100miles on i have full boost no shuddering at all.

I would consider trying this first, only £20 for new filter and around 1hours fitting ����

Pictures to show you the amount of dirt in fuel filter:
View attachment 29730 View attachment 29731

I had a similar problem with my wife's TDI 90 a few years back. Only it would almost die, especially on the motorway.

Had all sorts of scary diagnostics from the mechanic, including the intercooler and even the turbo.

But when he took the filter off it was FULL of black gunge like that.

I reckon it is from a bad batch of fuel from the supermarket we filled up at a few miles earlier.

It is always worth renewing the filter with symptoms like that.

The error code I was getting was an overboost one, which help confuse things, but I reckon that this error was caused because technically there was more boost than the fuel could supply. A tank flush and a fresh filter and it has never missed a beat since.

I am now going to say something while touching wood (sounds a bit rude that for some reason) but this has been the ONLY breakdown in any TDI across the 7 TDIs in our family, and that is over 16 years of driving A2s (and family driving) !!!!! Can you see why I lean my bias slightly toward the TDIs, but recent times the FSIs have grown on me a lot.

Steve B
 
Have you managed to change your fuel filter 'foghorn'?

Would be great to hear from you and see if this has solved the issue with your A2

Ross

Ross - Been away for 3 weeks and just back. I'm hopefully doing the filter change this Friday as I've got a couple of long trips to Scotland coming up.
 
Hi buddy,

As it has been mentioned before do not over tighten the plastic nut (10mm I think) even by hand can fluffy it, yours will be 13 years old so super brittle...

Enjoy, I get huge satisfaction out of repairing/maintaining my A2. And hopefully it will cure your problem. My car has been running Better then I can remember.

Ross

Or and post a picture of the inside of filter lid
 
I'm not now convinced it is the filter that causing the problem but I will look to change it anyway.

Went out in it yesterday for 2 x 15 mile runs at varied speeds and all was well running normal/perfect. Set off this moring for a trip to Coventry and the car started up as usual, then after about 10 mins on the motorway (warming up) the car went into 'limp' mode which feels like the turbo drops out and then started to stutter quite noticeably as if it was mis-firing. So I did the usual trick of ignition off then back on and that cleared the limp mode but still some erratic stuttering. Went into limp mode again. Repeated the exercise and cleared it which sorted things out. After that I would best describe it as 'semi-limp' in that I could keep it at 70mph and not lose power on gradients. Managed to do the 110 mile trip. During this I was getting no warning lights.

After a few hours for the retrun journey the engine started OK but rough idle/acceleration and limp. Ignition off/on and cleared with a few sessions of rough running/limp all the way home.

Leave the car 30 mins and need to nip out local. Car starts and drives a treat - perfect. Park up for an hour and returning home I get the same erratic issues. I'm now also occasionally getting the ABS/Traction orange light with the big red (!) in the DIS which I am presuming is brakes related and somehow triggered by the rough engine vibration.

Anyway you get the picture, it's erratic, inconsistent and only when the engine appears to be warm (not cold from overnight). This is leading me to think its an injector? or points to bad connections from the injector wiring loom as it appears to be mis-firing???

Any clues?
 
Last edited:
Hand on heart I had exactly the same symptoms...

Try the cheapest option first, fuel filter. If this doesn't cure then further investigation is needed.
oil misting around intercooler were alloy has split. Another culprit injector wiring harness...

I was constantly scanning my car with VCDS with no error codes appearing, other than one time I met up with Simon and I had a fault code 'P1556 - charge pressure control: negative deviation'. Simon cleared it and never returned. But I still had the symptoms. After driving 10,000 miles like this I decided enough was enough. I swapped air filter with a new one but no change, so I went and bought a fuel filter with doubt in my mind. But I came to the conclusion my engine was getting starved of air or fuel with having already change air filter it had to be this.
If filter didnt help I was going to have a fuel line flush carried out.

From now on I'll be changing fuel filter every oil change.

Let us know how you get on, and remember don't over tighten the small plastic nut!

Ross
 
Thanks Ross. Looks like I'll try that approach first and report back. Ever since I've had the car it will occasionally go into limp mode usually c2000rpm constant. However a stop/start has always cleared it and I've gone for months/years without it coming back so it hasn't concerned me. But now it's several times a session!
 
OK Chums - Update time.

I've changed the filter and no difference. Fuel filter was not dirty and very little crud in the cap. Car started perfectly after the change and as it warmed up started to stutter. Took it for a short drive and it's still hesitant/stuttering now most of the time. Turning off and then on will put it back to normal but only briefly before I get the same problems.

I'm leaning more to injector wiring loom and either dirty contacts or replace the whole thing, but as I'm not around for the next two weeks it looks like the job will fall to a garage - Vector @Northwich who were very helpful on the phone suggesting I changed the fuel filter myself to see if it sorts it. Ideally it needs a scan of the ECU to see what faults are in there as well.
 
Check out the crankshaft and camshaft sensors, especially if there are any errors that mention either.

They can sometimes only show symptoms when the engine is hot.

(sorry if you have already mentioned them?)

Steve B
 
Chaps an update now I'm back home and can scan the bill.

As I suspected from the start and as others directed the 'stuttering' fault was an injector issue. Before the strip down the garage thought it may need a new injector but would test it first along with a compression test. Fortunately the test on the injector came back sound, suggesting electrical the loom was checked over, connectors cleaned and rebuilt etc.

A scan picked up fault 'R01/Boost Pressure Deviation' and was identified as a hole in the intercooler. I suspect this is not connected to the stuttering issue but that has exacerbated what has been an occasional long standing issue where it would randomly go into limp mode. I'd lived with the very occasional limp mode issue since I bought the car as it could usually be resolved with a ignition off/on to reset it.

However now all is fixed and its running really well. Hopefully for the next 150k miles.

Top marks to Vector Vehicle Systems in Northwich (Cheshire) who were great. Very professional, good value and whom I can thoroughly recommend as they know the A2 well.

(Note: If anyone does require a new injector wiring loom I found them availavle here: http://www.darksidedevelopments.co....iring-loom-for-vw-1-2-1-4-tdi-pd-engines.html for £53. Turns out I didn't need one and you may get away with cleaning contacts)
 
Last edited:
Back
Top