apterr

We had unusually mild temps here (Buffalo/Niagara Falls) for the past two days, so... off with the car cover and out for a ride. Car started OK but within a mile or so drove like it was not firing on all 6 cylinders. Hoped it would clear itself up, so stayed within a couple miles of home for 10 minutes. Stopped the car, turned off the ignition, looked under the hood. Started the car about 5 mins later and the symptom was gone. Drove it for another 10-15 minutes and symptom never reappeared. Before I start it up today I wanted to get this out there and ask if anyone has an idea what this might have been (I am hoping it is behind me so I am using past tense). Thanks.
Andy T

1999Porsche911

Opening up the hood is always the sure fix for these things.

Most likely, the problem is behind you. Going to cold to warm creates alot of condensation in the engine and that may have been your problem. If you had actually been misfiring badly, you would have generated a CEL.

Tippy

Every now and then my old 996 would misfire right before full warm up. These engines use cold plugs for the high compression and I believe the o-rings on the spark plug boots were not holding up allowing oil to seep onto the plugs and fouling them. Check and see if you have wet plugs or oil leaking around the valve covers, could be your cause.

apterr

Not sure what a CEL is but if it is an engine warning display, it did flash on during the miss-firing episode. It did not come back after I re-started the car. Thank your for your reply.

lanny

cel- check engine light

Chads996

Sounds like the fuel has degraded. Make sure to put some of that gas stabilizer in the tank when you store it. Also, immediately go out an top off the tank with a fresh fuel.

C.

apterr

Thanks Chad, et al.

Chads996

No worries. Also, when spring comes...go out and buy some "Techron" fuel system cleaner. Great stuff. It will clean the injectors and lines. I usually do it every other 5K oil change.

C.

Ubermensch

Could be fuel as suggested. Might also be ignition related (plugs or coils). I had similar issues and it turned out to be bad coils. If the CEL tripped you'll have stored codes. You can pull them and see which cylinder(s) misfired.

apterr

Thanks, I drove it to work today (still relatively nice for Buffalo...Global warming effect I think). No problems. Wasn't aware the CEL stores the codes. I will have my Mx pull the codes the next time I visit him. I'll top off with new gas and add stabilizer today. Fuel system cleaner in March. Thank you

pat056

I can confirm. If you actually have a misfiring cylinder, CEL will come on quickly. Mine came on withen a minute. I didn't plug boot in completely after spark plug change.

apterr

If my CEL came on, which it did (it blinked on and off during my 10 minute ride) does that mean there is something wrong other than old gas? Thanks

Chads996

Not necessarily, you need to get the code read to be sure what it really is. Speculation won't resolve the problem. Don't forget, CEL's are primarily linked to the vehicle emissions sensor (O2). But again...go get the ECU plugged in and confirmed.

C.

gregorycarl

+1
Get it read before you do any self fixes. After all the snow you guys had and then really warm weather, tons of moisture in the air I assume. Electrical things poke -up if you had an emerging issue. Moisture in the fuel also like chad said...but pure speculation.

apterr

I will definitely get it ECU'd. Thanks a lot.
Andy T