Its not wierd because when you misfire, unburnt fuel/gasses are going into the cat and "shocking" it.

 

Thats good to know. I bought the o2 sensor already but im going to let it sit with the receipt in the box till I get this figured out.

 

ya you most likely wont need it. misfire codes are usually accompanied by 02 sensor codes if the misfire is severe enough.

 

Severe indeed. I just tested the ICM with a multimeter and the cycinder 2 pathway is totally closed. That would be it. I was however getting missfires in other cylinders too. Can missfires cascade like that from one cylinder or is it likley that I have a bad coil pack or two as well?

 

Ya its very possible the ICM could cause random misfires since it controls the firing order,and settle on a #2 misfire when its dead.

 

Ok, so I replaced the ICM the other day and got her running again. Was only getting like 15MPG and the O2 sensor code was comming back on. Ok, so I replaced that and I am getting about 24MPG 1/2 city & highway. now im feeling a bit better about selling it but I noted a small missfire when I was driving., No code though...

 

You may want to reset the ecu just to clean up and let the ecu re-adjust, and clear anything hanging around in the ecu.
Just pull the neg. bat cable for a few minutes. make sure you have your radio code.

Gald to hear the ICM and o2 took care of it for ya.

 

I used to have a 98' A4 that was chipped and the check engine light would ALWAYS come on. Everytime I went to the audi dealer to see what it was, the computer kept saying missfire in 3 and 4, and failure o2 sensor.It was a pain in my a$$ and never figured it out. Just selt with it for awhile until i totaled it, kinda happy I did cause that car was a lemon. Everything went wrong with that little f***er