FrancoPatria

Hello! I have recently bought a 2002 Audi A4 3.0 Quattro B6 and the CEL reads P0306. So I took out the old coil pack and replaced it with an aftermarket one and cleared the code. The next morning it is back on again with the same problem. So far, the light returns every morning (not sure if that matters). Are there any ideas on how to fix this? Thanks

jcman

did you check your spark plug?

FrancoPatria

No, what should I check for exactly?

Prospeeder

Well misfires will foul out the plug. I have seen where the plug builds up too much resistance and it will overheat a coil. Could be the misfire is not ignition related at all. Just blindly throwing a coil pack in isnt exactly the best diagnosis. What you should have done is swapped the coil between 2 cylinder cleared the code and see when it returns if it follows the coil to the other cylinder. If not you know its not the issue. Then do the same with spark plugs, injectors, and finally do a compression test. Could be a burnt valve or worn out camshaft.

jcman

Pull the plug out and take a look at it for a normal tan insulator and that the gaps are in range or intact, assuming that the plugs have at at least 50k miles if more than 70k you might consider replacing them all.

Prospeeder is right on with all said as this is what he does for a living, but the simplest method is the single effected plug test, if it don't remedy the problem move to next tests mentioned.