Multiple misfires. At Road America for weekend. Any ideas?

Monday of last week I drove my 2000 C2 to fill it up with gas. I got a CEL with code P0303 (misfire cylinder 3). I cleared the code, took a couple of 20 minute drives in the car with no issues and no CEL. Tuesday I loaded the car on my trailer. No issues. Wednesday I drove from Maryland to Illinois, then Thursday up to Road America. Friday morning before my first track session I drove the car around a bit. Shortly after starting the car, the CEL flashed a few times and went out. The car seems a bit rough at idle/low RPM. Well, I went ahead and drove all day. Five sessions out on the track. No CEL, no problems that I'm aware of. This morning I got the flashing CEL again right after starting the car. Again it feels rough at idle. I ran the first session on the track, and the CEL came on and stayed on (not flashing). The few points on the track where I was below 4000 RPM the car seemed a bit rough, but it smoothed out at higher RPM. When I got off the track I found P0300, P0302, and P0306. So, multiple misfires on different cylinders. The car has 96K miles, and I bought it with 85K. After purchase, I replaced the spark plugs and tubes. I did not replace the coil packs, and I have no record of them ever being replaced. I have also replace the fuel filter and AOS. After doing some searching on Rennlist, I bought some electrical cleaner and I'll try cleaning up the MAF. I also bought some Techron, and I'll put a bottle of that in the car. That's cheap and easy, so I figure worth a try. I won't be able to get new coil packs for at least a few days. I should probably go ahead and replace them, but would multiple coil packs fail at the same time? Any other ideas???

Do you have Durametric? I think replacing the coils is a great (and standrad) starting point. A fresh tank of gas will be good to eliminate bad gas too. If your scanner can read sensor values in real-time, you can check if the MAF readings are in spec.

Misfires immediately after filling up the gas tank strongly suggests "bad" fuel. That the misfires didn't persist though does tend weaken the "bad" fuel as a cause. But I think a fresh tank of fuel is a good suggestion. All the coils cover the same miles and pretty much receive the same exposure to the elements. That more than one can misfire at the same time therefore is not that surprising. My Turbo misfires on cylinders 3 and 6 occasionally, shortly after a cold start, but never at any other time. It is not due to coils but suspected sticky injectors. So simultaneous "failures" of the same component on different cylinders is not unheard of. Thus I agree with Ahsai that replacement of the coils is a good step. Oh, and a bottle of Techron is a good idea, too. BTW, the general rule is if one notices any improvement from running the first bottle to run a 2nd bottle. Also, another general rule or recommendation is to change the oil/filter after the Techron treatment is over with. The few times I've used Techron I have done so just prior to the car's oil/filter service so that at the time the tank of fuel with the Techron added gets low -- down to around 1/4 tank -- I fill up the fuel tank with fresh gasoline then book the car in for its 5K mile oil/filter service. I have first hand experience -- with my Turbo -- that misfires don't have to be plugs or coils. Even after new plugs and coils were installed misfires remain. The O2 sensors are "new", too, having been replaced in Jan. of 2015. So, if the misfires reappear after new coils and the Techron has been used up then come back for further discussion.

Cleaned MAF. Idle is smooth. Took the car for a 10 mile drive in the country. Smooth and no CEL. Back on track soon. Fingers crossed!

So much for crossed fingers. I did get one more good session on the track after my previous post, but during the last session of the afternoon the misfire returned and I headed for the pits. Looks like I will not bother going on the track tomorrow. I'll head back to the in-laws' place in the morning. First thing Monday I'll call the Porsche dealer in Rockford and see if they'll take a look at the car. I'm hoping to spend Wednesday on the track at Blackhawk Farms. We'll see if I can get the car sorted for that or if I'll be heading home early. By the way, I turned on the car once this afternoon, it was misfiring, and I hooked up my Durametric. It was showing multiple misfires on multiple cylinders. MAF looked OK. I shut it down, turned it on again, and it ran smooth, no issues. Once I figure out something I'll update. Thanks as always for pitching in!

Your symptoms are very similar to mine earlier this year when I took it to FL, the coolant expansion tank cracked, and dropped coolant on cylinder 1 coil pack....that lead to it's final demise. Once I had the new coil pack in hand and changed it out, no more issues. My misfires were pretty much identical to yours. I would start with changing all of the coil packs.

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That the misfires went away after an engine shut down and upon restart suggests an electrical problem. That the misfires are not confined to one cylinder and are in fact occuring in cylinders of both banks suggests a common (to both banks) failure point. This suggests the problem is with the MAF. It is electrical. And of course is a common failure point. (So's the DME but let's not go there just yet.) A MAF can go bad at any time. Often of course they last a long time. (I won't bore you with how long the orignal MAF in my 302K mile Boxster has lasted albeit with a short vacation as I replaced it after a mis-diagnosis of some fueling error codes.) But tracking is "harder" on the MAF. Obviously the engine is being operated at high RPMs and being asked to deliver close to and at its max power output. The engine is as a result using a lot of air. Thus the MAF is measuring a lot of air and this means a lot of current is flowing to the MAF to keep the hot film at the desired temperature. So it wouldn't suprise me the MAF is the culprit. But a new MAF is expensive and I can't say with enough confidence it is the MAF to have you run out and buy one. You are taking the car in probably today. Let the Porsche tech make the diagnosis.

Dropped the car off at Napleton Porsche yesterday morning. I informed the person at the service counter that I had gotten codes for misfires on multiple cylinders. They called yesterday afternoon with the diagnosis of a bad coil. That surprised me, given that I appear to have had misfires on multiple cylinders. However, I'm no electrical engineer! A coil pack is something I would typically replace myself, but given the circumstances (hoping to spend tomorrow driving at Blackhawk Farms) I told them to go ahead and do the work. I should know this afternoon whether or not this solved the problem. When I get home I think I will go ahead and order a set of coil packs ($375 for a set of six at Suncoast doesn't sound bad) and replace the other five. There are various places selling MAFs for about $200, so I'll get one of those as well.

Check with Jason at warehouse33auto if you're ok with using BERU OEM coils (made in Germany also). They're a lot cheaper.

I keep meaning to ask, will any MAF cleaner work or does it need to be a specific brand? I've got a P0112 error that followed the MAF when I swapped it between my two cars.

Check out warehouse33auto.com for the coil packs, probubly save you a few $$. If you put rennlist in the discount code box in the shopping cart, it will give yo an additional; 10% off as well LOL Ahsai must have been posting just as I was great minds think alike ???

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MAFs are relatively expensive parts for something that can be cleaned and tested. Have your shop check your MAF readings - if it's measuring proper volumes at idle and under load then save yourself the money. If the MAF was going bad, you'd have all kinds of fuel trim issues - usually involving 02 sensor codes being triggered. Also fairly easy to diagnose while they've got the computer "hooked up".

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Any MAF specific cleaner will work (CRC is a common one you'll find at any auto parts store). P0112 is complaining about the intake air temp sensor (embedded inside the MAF sensor). What car year/model you have? MAF is very model specific so you can't just swap them between two different years/models.

One C2 that was born in 2/98 and another C2 that was born in 3/98. Sounds like I just need to replace it then?

If you want, you can do some checking first since the MAF sensor is not cheap and may not be returnable. https://www.amazon.com/0280217007-99.../dp/B002IR3MD0 Unplug the sensor and check resistance between pins 1 and 3 of the sensor . Should read about 2.3k ~ 2.7k ohm. Then check the wire continuity between the DME and the MAF sensor plug: - Pin 1 of the MAF plug should connect to pin 15 of the DME - Pin 3 of the MAF plug should connect to pin 45 of the DME

Will do. Thanks Ahsai!

BTW, use only the Bosch MAF sensor (or the Genuine Porsche if you're insane ) The other cheapo ebay $30 ones are known not to work.

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Ahsai : Check with Jason at warehouse33auto if you're ok with using BERU OEM coils (made in Germany also). They're a lot cheaper. Thank you both for the continued support! -Jason

Car ran great at Blackhawk yesterday.

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Good to hear and a fun little track that a lot of people don't know about. -Jason

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So that's with the new coils? Confused.

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He had one coil replaced by the dealer before Blackhawk as I understand this previous post.

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Oh, right. I forgot that part. Thanks.

Too many racing threads going on in the regular 996 forums to keep track of it all.