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.

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.

[tcora]

Color me clueless, but how does a MIL code "flash"? Are you saying that the dashboard indicator flashes and then when you read out the code you see P0306? That code is a cylinder #6 misfire, for what it's worth.

[JFP in PA]

The "Check Engine Light" on any Porsche can simply light up, indicating a problem but not a serious one, or it can flash, indicating a serious issue has occurred and immediate attention is required. Covered in the owner's manual.

In the case of a DTC P0306, it is flashing because the number 6 cylinder misfire can damage the cats.

[aczyzewski]

Sorry, I see now that I wasn't clear. Should've put "P0306" in parenthesis.

[mikefocke]

Maybe start simple and see if the coilpack is on tight, anything else loose on cyl 6. Do you have the repair paperwork enough to know if the spark plug tubes were replaced?

[aczyzewski]

Thanks for the suggestion. Finally reached under the car. Coil packs seem tight. Of the on again, off again nature, right now it's running fine. In fact, last outing the flashing CEL was limited. Seems like it hits about the same time - 3 or 4 minutes after setting out. This time just once heading out and once heading back. Don't have a detail on what was done to the car prior to my acquiring it, but will see about getting that this week. Think I'm going to invest in jack stands, etc., and prepare to be more thorough with tinkering. Wonderful car. Having lots of fun with it.

[aczyzewski]

Update: Pulled injectors and took to RC Engineering for cleaning/calibration. Before: 2 dripping, 4 "good." After: 6 "excellent." Putting it back together this weekend. Changing spark plugs too. When pulling injectors, electrical plug on #6 cylinder (the offending, P0306) seemed a little loose. Will see what happens when it's all back together.

Update: Boxster back together. Runs like new. Much stronger, smoother than before. Hope I never have to put those clips back on the injectors... That took forever. Have to take it by the shop to have CEL turned off. Will see if that was it. Test run had no blinking. My conclusion: Probably loose clip on electrical wire running to #6 cylinder. Came off too easy. Nevertheless, happy I had the injectors cleaned. Had work travel to LA that allowed me to drop-off/pick-up injectors in person. Nice folks at RC Engineering.