P0300 Code - P0306 and P0305

[rogerjohnsen]

A while ago I was getting a CEL with P0300 / P0306 indicating a misfire on cylinder #6 of my car. The problem surfaced when the car was first started (cold) within the first 0 - 60 seconds during warm-up. I ended-up removing the #6 spark plug and checked the coil pack. There was a slight electrode gap problem with the #6 plug that was corrected to specification. Everything was re-installed and the problem seemed to have gone away. The other day I started the car and within 15 - 20 seconds, the CEL came on. The reader shows P0300 again with P0306 and this time P0305 in a pending state. I'm not sure the exercise I went through the last time actually fixed the problem as it seems to have re-surfaced.

Any thoughts on what else to check? I cleared the code and have driven it 4 times since then with no CEL's appearing at all. I notice when the car is first started, the engine seems a little "rough" obviously idle is a little higher until it warms up but kind of makes a quick "cough" when cold. I can take a video and post it if that be useful. The problem only occurs when the car has been sitting (overnight) and isn't warmed-up.

'04 996 TT

33K Miles

[Loren]

You can try swapping the coil pack to another cylinder and seeing of the fault code follows it. Likewise with the spark plug.