35 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHNot firing on all 6 cylinders?
Reported or suspected cause
behind you
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
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0
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Leading evidence: 'behind you' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'behind you' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Clean injectors and lines' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Reported cause
I had similar issues and it turned out to be bad coils.
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Performed · outcome unconfirmed
A 3.6L engine will fit, but there are other things that need to be changed/adjusted.
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Suggestion
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.
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Suggestion · Original poster
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).
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Outcome without a verified action link
You turn off the ignition, turn it back on, the CEL is gone and so is the problem.
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
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.
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.
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.
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.
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.
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.
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
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.
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.
+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.
I would get it to the dealer honestly. When i had the repeated misfire on my #4 cylinder along with blinking check engine light I ended up with a new engine in my 996. Good luck.
Damn, good for you. That's hilarious. I didn't even catch it the first time. This could be PAG's new slogan:
"Buy a Porsche and all your problems will be behind you."
Funny...
My '99 996 w/ 67,000 miles had issues very similar to yours. Whenever I turned off the motor and restarted it (groceries, gas station, post office, overnight at home), it would idle like an aircooled VW . Blip the gas pedal and it clears up. 4 days ago, check engine light came on. Tested at my local mechanic and cyclinder 3 had an issue. Coils bad. Ordered the part set the appointment date, and a day later, steamed up, overheated, DEAD!!!!!!!!!! Catastrophic failure. Now I'm deciding on whether to put a new 3.4, a used 3.4, (or does a 3.6 fit in there?). As it turns out, in retrospect, maybe the head gasket was going bad. Either way, it was just a matter of time.
Car has had no issues. Had several DE events at CMP, one at VIR. Darn, I wasn't even ******* it when it died on me.
Sorry to hear about your loss! That sucks.
A 3.6L engine will fit, but there are other things that need to be changed/adjusted.
Paul 996
recently replaced his 3.4 with a 3.6. Here is a link to his thread which will give you some info.
Replaced 3.4 engine with a 3.6 engine
Whizbyu,
Sorry to hear the bad news. Hope the rebuild/replace works out for you. Please keep me/us posted.
Best wishes,
Andy T
Tim, saw your same advice on a different thread. After 8,000 you just issue standard replies?
Well, I answered his question here first, and then I noticed he had started his own thread asking the same question. I wasn't sure if he would come back to this thread and see the link, so I figured since his question was repeated, I could repeat the answer.
Once I hit 9,000 posts, all of my posts will be one of the following 4 replies:
1) WTF? Where are the !@#$%^&* pics!
2) DAFS!!
3) RTFM!!
4)
I think that should cover 99.87% of all topics and I'll just ignore the remaining 0.13% of the topics!
This same discussion has been going on over on the 996TT forum....unexplained electrical gremlins that cause random misfires. You turn off the ignition, turn it back on, the CEL is gone and so is the problem.
Several guys have had this problem (me too). I finally sent it in to the dealership and they replaced the MAF under the CPO warranty. You can also go to AutoZone and borrow their reader....just take it outside and plug it into your car, read the codes, then give it back to them. The turbo guys are more prone to do the start/stop/start routine without worrying about catastrophic failures like some of the My99-00 3.4 litre guys.....There are a number of recurring issues that have surfaced for the 3.4 litre including the intermix issue, intermediate shaft, and pourous cylinders that seem to hit without warning and are not related to hard driving or abuse.... so ignoring the flashing CEL light like some of the TT guys have been doing might be ill advised.
Couldn't get it to the mechanic yet. Now there is snow on the ground so I will wait for a nice day and bring it to him. Will definitely get a readout soon as I would like to bring the car on vacation (Fla). and don't want to be "on edge" the entire time wondering if every sound I hear is the beginning of big problems. Thanks for the advice re: AutoZone too. My mechanic is in my family (through marriage) so I know he will treat me right.
Andy T
I wonder if you have a cracked coil pack. Condensation got in and interupted it, once driven and sat awhile it dried out and worked fine. Just a thought.
Brought the car to my mechanic. He said there were no codes saved. He put the car up and looked and felt around...nothing. He said the coilpack., plug, wires, etc. looked good. So... I will act as though it was bad gas and keep an ear out for any sputters, etc. If and when a CEL comes on I will take it to him immediately. Thank you all for your suggestions. Greatly appreciate it.
Andy T
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