Hello,

I have a 1998 a4 1.8t with a tap-1 stage 2 chip, custom exaust, k and n intake (no air box).

and all of a sudden with no warning, the car started to run rough, and had a loss of power.
when i pluged in the code reader, it gave me 2 codes, random misfire, and misfire on cly #3.

Here is what i have done.

i moved around the coil packs, to see if the miss followed the pack. it did not, still on #3
i pulled the injector rail to see if they were firing, they were.
i also moved the injectors around to see if the miss followed...it did not...still on #3
i did a compresion test, all around 125 psi....good for 80k
and yes i replaced the plug...

tap 1 is sending me a test computer
anyone have any other ideas??????
thank you in advance.....E

 

codes please

 

codes
16684 random

16687 miss on cly #3

and only after i started to do trubleshooting
16502 coolant temp (on and off)

 

i have the same problem going on right now..but its my second cylinder and i have 100k miles now..i dont have a scan tool so i brought it to a 3rd mechanic who seemed confident

 

well good luck to you,
you can be shure i will post the result with my car....hopefuly that might help you...
i am convinced that it is the ecu, or in the wire harnes leading to it...
we will see when the test computer comes in..

E

 

16804 cat below threshold
16684 random misfire that's normal
166502 now that's your problem a lose wire to ground signal obstruction, thermostat sticking or wiring problem

 

ok, i can accept that,
but when the problem first poped up that 16502 code was never there, even after a 15mile limp home???????

E

 

Bad ignition control moudle on air box.

 

that is what i am thinking, too,

 

I agree, i had the same issue on cyl. 2.

Replace the ignition module on top of the air box.