jinsoojoo

I have a 2002 Allroad 2.7T and I'm looking for the proper way to diagnose a P0304 code. I have done a search on the issue, but I don't see any posts from people with the exact symptoms I'm having.

Cylinder 4 is the ONLY cylinder throwing a code and MIL. Also, when the car sits overnight (or for several hours), it starts up just fine and runs smoothly. However, if I turn the car off after driving it for a bit, and then start it up again right away, the engine runs very rough and the P0304 Cylinder 4 misfile MIL code comes up. When the car cools down again, the engine runs smooth...

I have so far swapped the cylinder 4 ignition coil with on from cylinder 5 (still same code). Then I tried swapping the spark plugs (still same code).

Could someone point me in the right direction? Could it be an injector problem? If so, how would I check it or remedy it? Why does a blown head gasket cause misfiring? Could that be my problem?

Thanks in advance for the help!



P0304 Fault Code - Cylinder 4 Misfire

georgeb944

From the Ross Tech wiki:

16688/P0304/000772 - Cylinder 4 Misfire Detected
Possible Causes

Ignition system
Fuel injectors
Fuel pressure
Running out of fuel
EVAP canister purge valve
Evaporative emission system
Low compression
Base engine problems
Controle Module damaged

Special Notes

This feature search for engine misfire in a specific cylinder. Most of the time the cause for a misfire is a lack of combustion in a cylinder due to absence of spark, poor fuel metering, or poor compression.

GTA_Driver

What is the engine code? If your car has ICM (ignition control modules), swap them to see if the misfire moves to the other bank.

jinsoojoo

Thanks for your responses!

I indeed tried to switch the ignition control modules (ICMs), which are located on top of the air filter box. Sure enough, the misfire went from cylinder 1 to cylinder 4.

I'll order a new ICM and hopefully that will take care of the problem!