forum.audiv8.com Foren English Audi V8 Forum ECU problem ?

Hi

I've just changed my ABH engine on my Audi 100 S4 (the old one, with 214000 km was burning a lot of oil (3L / 500 km), the "new" one has 120000 km approx.)
From the old engine, I just kept the lambda sonde.

The engine is running well but I have a problem during acceleration : the engine is hesitating.

Instead of doing : vrrrrrrrrooooooooooouuuuuuuuuuuummmmmmmmmm
I have : vrrrrrr.....rrrrrrr......ooooooooo......uuuuuuuu.......mmmmmmmmmmmmmm (difficult to explain, it's not linear during acceleration)
I don't feel these hesitations beyond 3500 rpm.

With VAG-COM (not registered) there isn't any fault code. Maybe it'is a sensor, but vag-com don't let me to read them ! (I have a red error message instead of values : is it normal ???)

Maybe my ECU is deficient ?
Is there anyone who have an ECU to sold ?

Thanks

This sounds like a faulty knock sensor..
I had the same problem whit my Audi 90 20v..

Try to cleane the knocksensors connection remove corrosion and spray whit connectionspray.

If this did´nt help try to remove the knocksensor, cleane it upp and the surface, it has to be flush against the car.
Reassemble and re touqe whit about 10Nm

Some times these trix ill do the jobb, in my case the car was better for a while, but then i knew the problem and just relaced the knock sensor and after that the car turned upp fine.

Sorry for my bad English (I´m from Sweden)
I hope this will solve your problem...

Hi

I've tried to disconnect the O2 sensor.... It was better but this evening, the problem has come back !
So I tried to disconnect the MAF sensor...... the problem is less important, but still here
But, actually, now i don't feel anymore theses small hesitations during acceleration ... I just have some strong vibrations and hesitations between 1000 and 2000 rpm. But it only happens from times to times......
Sometimes, no problem at all !

I will disconnect the knock sensors .......

I have tried to disconnect knock sensors, the problem still exists.

Actually, hesitations and vibrations only appears between 1000 and 2000 rpm, on strong acceleration. Sometimes it also happens during small acceleration, and, very strange, sometimes, it doesn't appear at all.
The problem exist also when I don't drive, when I'm on neutral gear.

Where can it can from ?
I have a second engine for parts and I changed MAF sensor, injectors, fuel pressure regulator, spark plugs are new.
I will verify the timing belt and the "spark plug distributor" (don't remember the english word for this part)