My 98 A4 1.8T has #3 cylinder misfire. I bought a new ICM for $50 from MPG (Chinese part for sure) to replaced it. The part worked. Car started fine. NO more misfiring. Check Engine light went away after a day. But the car is lethargic. I thought it will take the computer a few days to get use to it. But after two week, it’s no better. I check the voltage coming out from the new ICM. It's the same as the old one. I am not sure replace it with an Bosch will help.

I heard that aftermarket ICM may not match the coil. Anyone has any advise?

 

the ICM only triggers the coils to fire. there is no learning curve associated with the ICM, it works or it doesnt. the car doesnt need to adapt to anything. you may have been put into limp mode which limits boost to 5psi from that misfire. the CEL going away doesnt mean that the ECU was reset and the code cleared, it just means that the problem isnt currently happening. the car doesnt know that you fixed anything unless you clear the codes.

what could have also happened is if you drove on it while it was misfiring you could have melted your catalyst so theres a big restriction in the exhaust now, that would also limit boost and power.

 

I hope it's not the catalyst problem.

Can the ECU be cleared (reset) with a generic OBDII scanner? or it needs a Ross-vag-com to do it right?

 

any generic OBD2 reader can clear it. were you driving it after the CEL started flashing?

 

I probably drove it another 20-30 miles with the light flashing....

The lost of power is mild. Usually when I go up hill. Gas mileage appears to be the same...

With no CEL, will scanning reveal any additional information?

thx for helping. I just spent $3K replacing TB, engine seals and steering. Hope this to go a little longer.

Geoff