Rough idle, then power loss and check engine light
 

I was driving my 2003 Boxster yesterday, while sitting at a light the engine idle seemed pretty rough. I drove off and the car seemed to be loosing power and running rough. After about 20 seconds the check engine light went on. I immediately turned the car off and coasted to the side of the road. waited 20 seconds, started the car up and it ran fine all the way home. I checked with a code reader this morning to see if there were any error codes, none recorded. Any ideas, a bad coil pack?

Thanks,

Dan

Restarting is never a good idea so you are lucky there (thinking IMS). However, one time I didn't have the air intake connected completely and it ran rough and died. You may want to check your MAF and the intake. On the other hand a clogged fuel filter can do things like this too.

Chris

A check engine light almost always leaves a code in the DME, what did you use to check for codes?

Well I changed the IMS bearing about 3 weeks ago with the LN engineering version, so I knew it was not the IMS. The engine light didn't stay on for more than a second or so, I literally cut the power to the car the second I saw the light. My friend brought over an OB2 reader that he bought recently, not the best in the world, but it wasn't bringing up any codes. Since this incident I've driven the car another 50 miles without incident. Any chance it could have been a clog in the fuel filter, issue with the fuel pump?

Dan

Could this be caused by a bad impulse sensor?

the same thing happened to me yesterday.

on off-pedal decel after a short, hard run, the engine started missing and the CEL was flashing. i pulled over but before i could shut off the car the idle was ok again and the CEL was solid. shut the car off, plugged in my code scanner and no codes (other than the O2 code that was already there).