Hey guys i have a 97 pre-facelift a4 with a test pipe i put in myself. i have the CEL mod for the 02 sensor in the back. i have the strangest problem however, my car is still getting a check engine light and it does not drive right at all. it idles very rough and i get a code that reads a cylinder 4 misfire. on acceleration there is absolutely no power until higher RPM's. Also, i can smell gasoline when this is happening. My belief is that the Front 02 sensor has an issue which causes it to allow an excessive amount of gas into the engine as a safety catch to not destroy it. Thus i have narrowed the cause of this to the front 02 sensor and have replaced it. while this helped for a little, it still has the same problem. I racked my brain and searched the web to try to find the cause of this with no luck, so i did what every aspiring mechanic would do: trial and error. I thought about how my rear o2 sensor has the CEL mod. while the front o2 sensor only measures gas, i thought i'd try loosening it to create space to see if that would do anything. the car started up fine idle'd fine and even ran good at first, but as the car got warm i started having similar problems although they were to a lesser degree. My question is this: has anyone ever heard of using a spacer on the front o2 sensor? also am i even going in the right direction? i could have just gotten lucky so i could really use your help. thanks!

 

What are the DTCs? If this A4 is a 1.8l turbo, the power output stage (aka ICM but I like POS because it is a POS!) is a suspect candidate among other things. I would not put a spacer in the front O2 sensor location that would screw up the fuel metering when you solve the problem of the misfire.

 

yea i would agree, but i didn't start having this problem until after i installed the test pipe.