130od judder / hesitation

[SebRogers]

My 130tdi B6 Avant has recently started to behave a little strangely under certain throttle conditions - and, as always, I'm looking for some insight from forum members more knowledgeable than me :D

Here's what happens. From very light or no throttle to gentle acceleration, occasionally there's a slight but noticeable judder / hesitation before the engine picks up and starts pulling. It only lasts a half second or so, it's subtle enough that I'm beginning to wonder if I'm imagining it, and of course it doesn't do it all the time so I'm left questioning my sanity even more :biglaugh:

It doesn't happen under hard acceleration (of if it does, I can't feel it), and it's most noticeable when applying gentle pressure on the throttle in gear, so I don't think it's related to gear changing. It seems to happen at a variety of road and engine speeds and in all gears. But only every now and then.

So... possible causes (and here's where my ignorance will start to show)? Engine mounts? Fuelling? Injectors? Something else?

And... would it perhaps be best to allow the problem to get worse, so that it's a bit more repeatable and easier to track down?

Thanks in advance!

[nutter1980]

Hi Seb,

I had these symptoms including occational cut outs when pulling away from traffic lights, Initialy was diagnosed as a faulty MAF sensor however 2 days after it was replaced the symtoms returned.

I then bit the bullet and took it to Audi, turns out my EGR valve/solenoid was gunked up, Audi advised they stripped the part and cleaned it out.

Never had the same problem again :) Also I think someone on this forum recommended that it should be inspected or cleaned/replaced every 20,000 miles.

However Im no expert !:D

[benjie]

As above sounds about right, but I would say 60000miles or m ore for the cleaning bit - depends on many factors though - typre of driving, frequesncy of driving, fuel quality etc!

[SebRogers]

Thanks guys. From doing a bit of reading around it appears there are a large number of possible causes, of which a sticky EGR could certainly be one. But given that the effect isn't even close to repeatable, I think I'm going to have to just keep an eye on it until it gets worse / more consistent, otherwise I'm likely to be chasing my tail.

Thanks for the input though. Always appreciated :beerchug:

[Marco34]

I've had the sam thing recently. It returned. Mine was about 2k rpm in 3rd and then it was like a boot in the back as it kicked in. I do alot of short trips to work and not really given it much action recently. Car that is... ;)

Anyway, I put some forte in and happened to be going to Yorkshire a few weekends ago. Some steap hills ad some heavy throttle use has shifted it. My thoughts are the egr. I had it on VCDS and performed outputs tests prior to going. I'd try and additive and give some mixed driving... ideally some hard runs if you don't normally.

These engines are tough and seem to drive better after a long run on the motorway and some acceleration.

:beerchug:

[SebRogers]

Thanks Marco. Working on the assumption that it's most likely to be related to fuelling, I'd wondered about giving the fuel additive route a bash. I drive the car with economy in mind 90% of the time, but make full use of the engine when I have the opportunity... so it should have a chance to clear its lungs from time to time :) Of course, I have no idea how the previous owner drove it...

I'll give it a go.

Anyone know how much (roughly) an EGR cleaning is likely to cost at an independent? (and before anyone suggests it... realistically I just don't have the time, inclination, tools or knowhow to do it myself).

[nutter1980]

Seb,

My local indi was stumped and could not figure out what was wrong, I took it to Audi who charged me £70 to clean it out.

Probably cheaper at an indi..

[SebRogers]

OK, thanks for that. At least it's not a particularly expensive job. Forte first, I reckon, then see how it goes...

Cheers! :beerchug:

[Marco34]

I would. It may be that it would ideally need a clean out but if you use decent fuel and use Forte every 6 months or so it may keep the problems from appearing. Mine is 8 years old this year but only 43k. I may tackle an EGR induction clean this summer!

Let us know how you go with it. One thing I've been advised by many techies who use Forte is to get a low tank then add the whole bottle and put about £20 on top! Not 50 litres as on the bottle. Why I don't know, they just say it's better and even bypass the fuel filter and use it neat on really poor cars.