My A6 2.8 is getting codes P0300, P0301, P0302, P0303 Misfire - and the check engine light blinks. I believe this is a misfire and I believe the blinking light means the Cats can be damaged.

Anyone know what would cause this?

What cylinders are 1, 2 and 3 and how can i test the problem?

 

Don't drive the car, 1,2,3 are the passenger side bank. I would check the wiring harness for the coils and for the injectors first also take a look at the T-belt. Did you use a vagcom to pull the codes? because my generic one won't pull them all. You may have more codes than that.

 

I thought their was only one coil on this car, 99 A6 2.8 30V - Why should i not drive it, do these codes mean the Timing chain is shot? Can it just be that the plugs need relpacement.

 

since you are getting those codes for cylinders 1, 2, 3 something is wrong with that bank and driving the car WILL damage the cats, which will get pricey. For you to have a misfire on all 3 of those cylinders there could be an electrical problem like Jackmup said or the timing belt could have jumped a tooth causing this.

If you havent changed your plugs then you can try that but it is unlikely that it is causing a misfire on one bank.

 

And the rule of thumb is to not drive the vehicle at all when you have a flashing CEL. That's when you know it means business.

 

I think the 2.8 just has one set of 3 coils, using 'wasted spark' to fire 2 cylinders at the same time. If the coilpack was bad, I doubt it would fail on 1-2-3 only - I would expect to see problems on the other bank too.

Misfiring checklist:
Spark
Fuel
Compression

Spark: On one bank you could have bathed the plugs in oil due to a blown valve cover gasket, but any other ignition related problems would cause problems on the other bank. Ignition timing related problems would have another code and are unlikely since all it needs is the crank position and it would not run if it didn't have it.

Fuel: The injectors all come from a common fuel rail, so if pressure was failing, the other bank would be affected too. Short of having a wiring problem I can't think of another reason why a whole bank would be affected. This would give you a different code though.

Compression: If, big IF, your timing belt is off on one bank, it would cause a misfire only on that bank. Your camshaft position sensor would be complaining though and you would have another code. You can double-check by searching for the timing belt DIY instructions and looking at the pulleys to make sure it is all in time.

I might be wrong about all of the above, but those are the steps I would take.

Good luck!

 

You should have your car towed to a mechanic. Use a flat bed service.

BTW;The engine does not have a timing chain it is a belt that wears out.

 

When i reset the codes codes, it starts and runs great for about 5 minutes, then when it warms up, it runs rough at idle (when i come to a stop light) , then the check engine light comes on and blinks (Codes P0300, P0301, P0302, P0303).

Same thing today. Any ideas?

 

If it runs great to begin with, you can rule out mechanical problems. Pop the plastic cover off the cam cover on the passenger bank, pull out an ignition wire and see if it has oil on it.

Driving with a misfire means that your cat is getting a bath in cold gas - not a good thing to do when it is at operating temperature because it will have a quenching effect, damaging the substrate. For troubleshooting it is necessary to run the engine a bit to see what is going on, but don't go for long drives.