Poor turbo performance

[tony-t102]

Hello chaps. Any help with this would be really appriciated.

I have a S2 Avant which has covered just over 100k miles. When the turbo comes in, there doesn't seem to be much power. The problem is very intermitent. Sometimes, I will feel and hear the turbo start and the power will be fine, but then there will be a small flatspot in the acceleration.
I don't know if this is connected, but when the engine is cold, when I depress the clutch and make the engine idle, it will sometimes try to stall. It's only cut out once but all the other times, the revs dip down to about 200rpm and then overcorrect themselves and shoot up to 1500+rpm for a second or two. After that, they are fine and sit at around 700rpm.

Any ideas?

[Greg_S]

could be your lamda probe contributing to problem

[tony-t102]

Yeh, I thought about that, but it was replaced about 6 months ago.

[Honahon]

boost leek or MAF sounds like to me.

[GandalfS6]

boost leek or MAF sounds like to me.

I agree, the power problem can be MAF or boost leak related. The idling problem, however, worries me. The throttle potentiometer and the idling switch is in the same unit - it sounds as if the idling problem could be the idling switch not kicking in. If the unit is faulty, it might also give the ecu incorrect throttle angles which could cut the boost.

If you have access to VAGCOM, check (with the ignition switched on, but the engine not running) what the maximum reading is for throttle angle (Group 3)- it should be between 90 and 99. You can also check this using a multimeter.

When closing the throttle (once again without the engine running) you should hear a click coming from the idling switch. You can also test with a multimeter.

I can look up the resistances if you don't have access to VAGCOM.

[Pete_RS2]

Boost leak sounds favourite. Have you got a boost gauge fitted to see what level you're getting ?

Idle problem could be Idle Stabilisation Valve. Try cleaning with carb cleaner or similar.

[tony-t102]

Cheers guys.

If there was a boost leak, wouldn't this happern all the time instead of intermitently?

Excuse my ignorance, but what is MAF? I've never had a turbo Audi before and I'm not too clued up on them. It took me ages to find this one.

Cheers again chaps.

[s2-1.5bar]

Hi

MAF is air mass sensor. The thing that situated between air filter box and turbo inlet. Piece of black plastic pipe with some wires inside and connection outside.

Cheers

[Honahon]

Mate- ive got a boost leak, and it's a ****** to find (spent all day today trying to track it down to no avail!) boost leaks (ARE / CAN BE!) intermitent - turbo will come in then drop out again.. I maybe wrong but the ECU can cut in (over boost protector or something like that) there's loads of guys on here that know allot more than me, but that's a basic answer. Try cleaning your MAF first - if you do a search theres some great step by step threads to walk you through the process.. it's very easy.

Good luck.

J

[newsh]

How about a sticky ISV? that can cause idling prbs, had it on mine recently, take it off, wash out thoroughly with WD40 and put back again, easy.

[newsh]

Hmm, does soumd like a boost leak though..