Having a serious problem diagnosing a misfire. Get a code of "cyl 4 misfire: P304". the engine is misfiring only in one cyl, #4

I've checked the compression, coil pack and changed it, check'd elec current flow and wiring, plugs, ignition, etc. I've cleared the code and restarted it and the code returns when restarted. I've swapped injectors to other cyl & code re-appears.

any ideas?? I've been working on audi's and vw for 25 yrs and this one has me stumped.

thanks

 

I have a similar problem,

P0308 Cylinder 8 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0300B Random- Multiple Misfire Detected

I have swapped Spark plugs, coils, and injectors and the codes returned anybody?

 

What year A8? Pre 04 A8's sometimes have problems with building up carbon the intake valves that can sometimes cause a miss-fire fault. A re-flash of the ecm would fix the problem but since there isn't one currently available that i know of try the old school fix and spray chemtool carb cleandown the intake trick.

 

have the same problem on '96 a8 3.7 v6. Also cyl 4. coils and plusg and wires ok. Any solution? Perhaps bad ICM? You suggest valve is stuck open or close? i mean due to carbon build up?

 

What were the results of all these tests? Does the injector get power from the ecm? You may also want to try disconnecting coils on different cylinders to make sure number 4 is the one that is actually misfiring.

 

I have similar problems with my -97 A8. Cylinders 1 & 5 reports misfiring. Changed plugs, took it to Audi quick service, but they just told me that they have to do more extensive investigation (and more money). Going to change coils next. Hope it will fix it.... :-(

 

my a8 3.7 has same problem on number 4 cylinder.changed coil pack,injector,compresions r all good.same as all other on this thread,has anyone found sollution yet??

 

Try swapping the ignition control modules and see if the misfire changes to a different cylinder.

 

o2 sensor?

 

Changing the ICM solved my problem. However, i have a huge fuel cons 19-20l/100