I just replaced my o2 sensors, and now when i start the car after about 15 senconds it feels like the engine is missfiring for about 15 seconds, then it instantly goes back to normal idle. I now have a CEL, but the scanner at autozone doesn't bring up any codes. any clues?

 

You sure the new 02 sensors are plugged in at the harness?? If it just started happening give it some time and then recheck for codes. Or try to find someone with vag com, i wouldnt trust an autozone scanner further than i could throw it... Well.. I guess i could throw it pretty far, but you know what i mean.. Give it about a week. But if you have a CEL, there must be a code stored already. Try to find vag throught the vag com locater link in the audi links.

 

I never unplugged the harness. I bought the new o2 sensors without a harness and soldered them in.

 

Is there a "hot" wire on your new sensors? Most newer cars have 02 sensors that heat up before the engine has reached normal temps to help emissions at startup. Some generic 02 sensors dont have that. You sure you soldered the right wires? I personally would have gotten a direct replacement from ECS or whoever that indludes the harness. If your soldering points are too big or messy that can have an affect on the sensor's performance. You could try resetting the ecu i guess.

 

I agree. Your heaters for the o2's arent working. You either have them hooked up incorrectly or they are the incorect part. The only universal thing about universal parts is that they dont work on anything.