CEL (P0306) intermittent flash at start

[aczyzewski]

Would anyone be able to explain why a CEL (P0306) would flash intermittently (meaning flash for a bit, then steady, then flash some more) during the first few minutes of operation (couple of miles) then remain steady? Another oddity: more often than not the engine runs smooth; have a few situations where rougher, misfire-like running occurs, but then it will go back to smooth a few trips later. This doesn't happen mid-trip but after a stop over.

Thanks to this forum, I've read quite a bit about the many things that could be going on. Just thought that these symptoms might help prioritize a plan of attack. Recently purchased the car. 44k, looks great, recently worked over by a quality independent shop. Was told previous owner didn't drive it enough or hard enough and carbon build up caused it to quit running. They claim they put 6k or 7k worth of work into it so I assume it's tuned up. Car has no other issues.