What does this sound like?

[UrS4Eben]

Hi guys.
I had a bit of an issue driving to work this morning and I'd like to hear your thoughts about what it could be.
Car drives pretty normal at part throttle.. no strange noises etc.
but...
when i put my foot down and its still under 3k rpm, the boost goes up to 2 bar on the guage but the engine doesn't seem to speed up and when I let go of the throttle, it gives a jerk before going back to normal.

My first thoughts.... fouled plug of dud coil (Apikol conversion).
I had a dud coil when I bought the car but I remember more of a shudder at WOT than there is at the moment...

Any input appreciated.

[Rusty]

Sounds like the knock sensors are coming into play or you have a boost leak.

Might be worth checking that the plugs are in good condition and are all secured correctly.

[UrS4Eben]

Because of the lack of shudder I was thinking boost leak too.. but would the guage still show 2 bar in this case? Where is the boost measured that displays on the OEM display?

[Rusty]

Whenever I've had a leak the gauge has fluctuated, if it's steady then possibly not.

Have you changed from 98 to 95 petrol? I used to have severe problems, very much like this when my Dad forgot to put in 'expensive petrol' (bloody Scots!) and put in some "nice and cheap" Tesco 95 "stop complaining, I've paid for it". Car ran like it was pulling a tank. After replacing the lambda probe this went away.

[UrS4Eben]

I use 95 most of the time (cheapskate South African ... The boost is not fluctuating... hmmmm I pray i will find a loose coil or a cats whisker in one of the plugs or something..

[Rusty]

Change the lambda if it's old.

[UrS4Eben]

Could a dud lambda cause this? I mean its a good idea to change it anyway but could it be the cause?

[Rusty]

As I said before I had a lot of strange goings on with a crap Lambda probe, it confuses the ECU and causes problems on WOT as well as during mixture adaptation, these were solved with a shiny new one.

Anotehr option is a dirty or faulty MAF...

[UrS4Eben]

Thanks for your suggestions Andy. I'll do some diagnosis before I ask anymore questions.

[gedu]

My car did that. On part throttle response was nice etc, but on full throttle something was missing. Ran without shudder and sounded quite normal. On dyno things started to unravel. First "power" run yielded under 200hp :S

We started to rummage around the car, and found cat innards in exhaust y-pipe, 20cm from exit. Dismantled exhaust, cleaned it, bolted back together, no problems anymore.

So, long post, but wanted to tell the tale Check your exhaust for blocks.

[Heat Seeking Missile]

I've just replaced the lambda on mine but it was rubbish at anything apart from full throttle. Still boosted fine though. No harm in changing it anyway as a precaution.

Mark

[k.alle]

Will be following this thread closely as my car has some of those behaviors too.

I have a slight juddering on the boost gauge on some occasions but no boost leaks.
Holds up to 1.5bar just fine, the hoses get pretty stiff @ 1.5bar

I have only felt the raw power of the S2 about 3-4 times in my year of owning it.
Sad really.

[UrS4Eben]

Well there was not time last night to check anything yet unforutunately but after going to the postoffice now and winding the window down there is a hisssing noise coming from the car on boost..... something tells me that if it was a boostleak, it wouldn't be showing 2 bar boost in the first place... The lack of shudder tells me its unlikely to be an ignitions problem... so now the top candidates for me seem to be:
1. Exhaust(Thanks Gedu would never have thought of that)
2. Lambda

What are your guys thoughts after the new hissing info?

How would I do a DIY boost leak test?

[Fat Audi 80]

For gods sake run it on 98 for a start. These cars *will* run on 95 be don't like it and that should be your first port of call!

It does sound like a small boost leak. A large one would be obvious, the power would drop suddenly.

Cheers,

Steve.

[UrS4Eben]

Can someone point me to someone that has the TCS146 Samco kit in stock?
I really don't feel like waiting 4-6 weeks....