2000 911 misfiring issue...

Hi I am new to this forum and having a Porsche but this seems to be a great forum. I am posting because I recently have had a misfiring problem with my 2000 911. I first noticed an issue when it was up to temp at low rpm's. I got home and it threw codes p0301, p0303, and p0305. The car has about 78k and the 60k service was done on time replacing fuel filter and plugs and all that good stuff. I haven't been driving the car. I just cleared the codes and fired it back up and it came back with p0301 only. It was misfiring kinda bad so I didn't take the time for it to warm up and have not driven it to see if other codes would pop up. Any info would be greatly appreciated. I plan on taking it to the dealer Monday next week if I can't figure this out and fix it myself. Let me know if anyone has any suggestion's to help diagnose this. Thanks for looking and any help! Jesse

Coil packs ever been replaced? Show us your Porsche pics so we can help you with your misfire, welcome to Rennlist.

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Whenever I read about engine misbehaving appearing after the car has not been driven for awhile I think of rodents have been at teh car, at teh wiring. (I was in a dealer the other day and came upon a car in for rodent damage. The check engine light was on. The code pointed to a problem with the gas tank vapor recovery/ventilation system. The tech removed the panels under the car that exposed the small tunnel that the coolant pipes run through and on top of one pipe is the vapor line that runs from the tank to the engine. The mice had gnawed through this line just enough to create a small air/vapor leak. In another case, some months back, another car was in with engine misbehavior (I do not know if the engine was misfiring) with check engine light on and the tech found in this case rats had been at/in the car and had gnawed the engine wiring harness which was causing the engine to misbehave.) If you can find no signs of rodents -- check the top of the underneath plastic panels for rodent sign/nesting trash -- then the coils are suspect. As is the quality/freshness (even the seasonal blend) of the gasoline in the gas tank. Sincerely, Macster.

When I say the car hasn't been driven, I mean only a few days. Its driven just about daily, just not since the misfire. It just started the misfire about a couple of days ago. I was thinking the coil's as well. I just wasn't sure if that made sense because it said cylinder 1,3,and 5 where all misfiring. Is it common for more than one to go bad at a time? I will fill it up with gas and drive it around and see if I can get any other codes to pop up. As of now its just cylinder 1 since I erased the codes. Also what kind of pics would be helpful? I have not taken anything apart as of yet.

This is confusing. I just took out the car got it warmed up and topped off with gas. Got home and scanned it and now it says p0301 and p0304. Only misfiring at low rpms and idle. Any ideas?

It is customary to post pictures of your car prior to asking for help. Sorta introduces you to the community. What part of the country are you in and do you keep the car in a garage or outside.

Gotcha. The car has been in Florida the past year I've had it. Garaged most of the year but driven almost daily. I just moved to Kentucky last week. During my move when I drove it here, it rained the whole time. Im not sure if that has anything to do with the issues Im having now, I just figured Id mention it.

When I was searching for my cab, that is the color I was looking for....beautiful. My money is in the coilpacks, specially since you mention the rain. -P

Rain can be a culprit! Thats why I asked. Thanks for the pictures. Welcome!

Here is the misfire troubleshooting guide: http://www.renntech.org/forums/index...ttach_id=24613 Lots of good info in there, plus page 6 has the coil pack troubleshooting guide. Misfires can be caused by a number of reasons, some of them will produce other DTCs (codes), and some will not.

I just replaced all 6 coil packs and spark plugs and cleared the codes. I started it back up and the code 0301 came back immediately. Does it take a while for the ecu to recognize the change or should it be fixed instantly? I only had time to let it run for a couple of minutes but it was still missing.

I have a similar problem that my mechanic is looking at but with me it is all in one bank and only misfires about 5k rpm. Coils check out, fuel injection looks good, timing looks good, spark plugs were just changed again, and MAF is new. So it's a head-scratcher for sure. I'll keep you posted when I find out what the cause is.

Not sure where you are in KY, but if you're in or near Louisville, I recommend Stuttgart Specialists as a good independent shop. My guess was the coil packs....

i would have guessed coil packs/spark plugs too - but those are new. hmm. i had a similar experience with my c4s. misfire cyl 3. right after spark plug replacement. i was lucky. the conector had worked its way loose (never put on properly...). i cleaned it, reconnected it and no problem. keep us posted on your progress. good luck

(coil pack connector)

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If the coil was the cause of the misfire replacing the coil should have not resulted in another misfire code. The Ecu constantly checks and rechecks for misfire conditions so if a misfire code is logged it is not due to stale info. There is a slim chance the new coil is bad, or mis-installed, so it might be worth the effort to swap the 'bad' coil with a good one and of course be darned sure both coils are installed correctly then see if the misfire follows the coil or remains with the cylinder. If it remains with the cylinder.... what did the plugs look like? Any notable differences between the plugs? A misfire that occurs and is not related to a bad plug or coil could be a burned valve, or something in the valve hardware, a bad lifter or a cam lobe that has gone flat. Unless you find something external to account for the misfire I think you might consider a compression test and possibly a leak down test. There's a problem and one/both of these tests will help you and your mechanic narrow down the possible problems. For instance if a leak down test finds the cylinder not holding pressure then a listen at the intake and exhaust can help one decide if the problem is with an intake valve or an exhaust valve. Sincerely, Macster.

Its fixed! Thanks so much for everyone's help and input. The coil pack connector on the 1st cylinder wasn't clipped into place and the connection wasn't good. I saved $600 compared to taking it to the dealer so thanks again!

Great news!

I'm so glad I'm going to drive my Porsche tonight in celebration for your 'fix'.

Apparently my car is not fixed. I put it new coils and plugs and re-checked the plug connections. The car ran well for about 2 days and now Im randomly getting different cylinder misfires. The original coils are part number 996 602 102 00 beru 0040 100 021. The new ones are 997 602 107 00 beru 0040 100 031. I think this new number just replaced the old one? Am I correct here? The service manager at the dealer said they weren't porsche coils and they needed to be changed again, but I think he was an idiot. Does anyone know what could be the issue here? My recent codes are P0300,P0301,P0306. But they keep changing around. The dealer pulled codes 301,303,305, and 306. This is very confusing. Im going to take it to Stuttgart Specialist's next week if I cant figure this out. Any input if much appreciated. Thanks again.

The latest (replacement) coil P/N for 996 is 99760210700 for 99-01 and 99760210400 for 02-05. I suggest following the misfire troubleshooting guide I posted earlier religiously. Since your misfires are on both banks and seemingly random, I would focus on common items such as MAF, DME, intake leaks, proper installation and type of of packs/wires/plugs.

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Hard to imagine if the coils were new and had the correct part number that clearly indicated the coils were for your car's model, at least at some point, that the coils could be the the cause of the misfires. The dealer is just (probably) going by the book and that is the car's VIN is used to look up the part numbers for the coils and 997 602 107 00 comes up and if the coils you are using do not have that part number (and if the engine is manifesting misfire error codes, random codes that often are due to bad coils) that the dealer is going to say what it said. OTOH, even though the coils you bought have the right number they may not be the same coils as they were some years ago. Porsche may have moved to the 997 coils simply because the coil maker changed something and the coils with the otherwise right but older part number are no longer are suitable. The parts department managers I talk to always tell me to when I want to order parts for my Porsche cars to order them based on the VIN. Porsche ties parts numbers to VINs and over time parts either go away, or are replaced by parts with different numbers. Also, I know many do not like to read this but I often have my doubts that discounted parts even though they are claimed to be the same as 'factory', are actually that, that they have have the same characteristics and quality that the parts handed to you over a Porsche parts counter have. To state the obvious, you have to eliminate other possible causes of the misfires or the coils become suspect. Or you replace the coils with the 'right' coils and then go from there. Added: The misfiring may be caused by say improper fueling. This may arise from a bad air intake temp value (this comes from the MAF) or from a coolant temp sensor. If the temp reported by the sensor is higher than actual the DME will not provide a rich enough mixture for the cold engine and misfires can result. If the check engine light doesn't flash the misfires aren't severe enough to put the coverters at risk of overheating from unburned fuel from the engine being combusted in the converters. You can disconnect the MAF from the wiring harness, clear the codes to clear/reset all learned fueling back to their defaults, and start the engine drive the car as you have in the past to see if the symptoms/codes reappear. Or you can with an OBD code reader/data viewer/logger view the intake air and coolant temps at cold engine start and compare them to each other and ambient and if you spot any big differences in readings the reading furthest from actual points to the suspect sensor. Sincerely, Macster.