Hello! This is my first post to this thread. I didn't locate anything similar to it so here I go...

2001 Honda Civic LX - 5sp manual - 302,000 miles. I replaced the head gasket (myself) at 300,000. Had head checked and milled at machine shop. During HG replacement I removed head and left timing belt in (was replaced not too long before). I marked belt and top cam so I could place belt in same position when reassembling. Anyhow after I got everything all back together I started car. It had a rough idle and started throwing mainly a P0303 (sometimes a P0300 - P0304). I replaced plugs. No improvement. While the car was idling I disconnected coil pack on cylinder #3 - idle did NOT get worse. I replaced coil pack. No improvement. I replaced fuel injector for cylinder #3. No improvement. Car seems to drive just fine as long as I'm not waiting at a light. At idle, idles rough and check engine light eventually comes one. I have tried resetting the ECu each time as well to relearn idle. I have stored the OBDII codes if that will help.

ANy thoughs? Could it be a valve issue in cylinder #3 (I plan to run a compression test)? Possibly bad ring (it was running fine before HG replacement).

PS: I have NOT yet cleaned the IACV. I can't see how that would cause a P0303 though.

Thanks
Brian