My car is a 2000 S4 automatic with 137k miles. The car was stock except for the darintake (sp?) prior to the APR stage I ecu upgrade (93 octane). It ran perfectly fine with the occasional downstream o2 sensor CEL. It would come and go and didn't sputter even with that code.

I got my ecu back last thursday and I put it in and she ran like a bat out of hell. I took it to work on friday which is 4 miles and it ran perfect. It started sputtering under full boost on the way home. No CEL, but I decided to change out the plugs with some Denso Iridiums (IK20's) on saturday and it started sputtering again after about 5 miles.

Sunday it threw a P0102 CEL code which is Mass air flow meter fail or large air leak (or something like that). I cleaned it really well with MAF cleaner twice and still the same. Also did a leak test with my compressor and no leaks at all. So I ordered a new Bosch MAF from ECSTuning. Came in today and I replaced it and still sputtered. I went to drive to see if it would throw a code again. The CEL started flashing soon after I went to full boost once and stayed on. Went straight to Advanced auto which was 1/4 mile away from where I got the CEL thankfully.

They read it and it was a P0303 (Cylinder 3 misfire detected). Drove it straight home and now it sits there. The sputtering felt exactly the same with the old/new plugs and the old/new MAF.


I am going to check that cylinder tomorrow or sat. Couple little notes...the exhaust is now blowing some smoke (couldn't tell the color since it's night time) and I didn't try adjusting the spark plugs since they have the iridium tips (i've broke one in the past trying)

Sorry if that was long winded. But I wanted to paint a picture for anyone that reads this and might be able to help me out as to this whole timeline of events. I did a lot of research during this whole ordeal. I'm open to any suggestions as to why this happened and how to fix it.

Thanks!!!

Andrew

 

Update: So I checked the compression and it was just fine thankfully. So I decided to swap the #3 coilpack with the #2 coilpack to see if I would get the CEL for misfire on #2. Well I drove around to see if the CEL would come on and it didn't sputter or anything. No CEL and it ran nice and strong. I'm at a loss as to why everything is fine now. But, I'm just fine with that!

 

Glad all is well...you probably just had a loose plug wire. At least you have it narrowed down to either the coil pack or the wire if the code reappears.