Running rough.....

Hi and Merry Christmas everyone, I got a new interesting problem with my -00 996 today. I was leaving for a Christmas dinner, and when I started the car it ran on only 4 or 5 cylinders. I left the house anyway, thinking it would clear up when I drove it. Stupid, I know. I drove it for three minutes and then decided to turn around. It ran very rough, and it didnt help to rev it. So I parked it, and when we came back now I tried again. It started rough, but cleared up after a few seconds. It still hesitated when I revved it from idle, but othervise it is fine. Anyone know where I should start to look? I should mention that it ran great before I parked it two days ago. I had just taken it out on an hour long spanking trip. The weather have been very moist here, and unusually warm with 45 degrees F, when it ran rough. Within 7 hours the temp dropped to 28 degrees, which was the temp now when I tried again. Could that point towards ignition cables? The strange thing is that the CEL did not light up. I was thinking that some PO had disconnected it, since it does not light up when I turn on the ignition. Should it light up? Thanks, Johan

I would look at the spark coils. You probably have one that's cracked and moisture made this happen and then once you drove around a bit it dried up some and got better. This happened to me and that was the reason. Once you unbolt the heat shield these are fairly easy to get to. For the 2000 I think it also has tubes that go around the spark coil, so if you replace the coil then you'll need to get the tube. It also could be that some moisture got in your gas and you were running through it. Those are my thoughts. Merry Christmas! I hope that your problem is fairly simple.

Yes CEL should light up when you turn key on. Cylinder full of anti freeze? Flashing CEL? Sure you fixed that intermix? What do the plugs look like? Any stored trouble codes? Cracked coils? Merry Christmas!

Yes Logray, that would be a nice Christmas present! But, no smoke, no intermix besides the few drops that still find its way from contaminated parts of the system.... Is it even possible to disconnect the CEL? I am not convinced there are small light bulbs back there, I would guess it takes some skills to remove it. I will start with the coils, thanks! Thanks, Johan

Thats scary. This makes me want to check out my car now. Hope everything works out for you bud. Merry Christmas!

Did a more thourogh check. These lights dont light up when turning on the ignition: Lid open varning light Check engine light PSM lights Safety belt warning Rollover protection warning light Taken from a 2001 manual but I would guess they are the same. Looks like I have to pull the cluster! Johan

So, we are back in the mid-40ies today. Went out to my 2005 F150 to go over to my storage and pick up some parts, and it is doing the exact same thing as my 996!!!! only it is running on 6 or 7 cylinders.... CEL is blinking on it, though. And, it starts to run smooth after ony 5 minutes. Johan

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Any UFO's in the area? Why would BOTH cars do that at the same time? Scary!

Did you happen to fill up with fuel from the same location on both vehicles? Sounds like a bad batch of fuel!

On early instrument clusters (1998-2001). There are bulbs. They are pretty easy to replace actually. I hope it is something simple like a coil pack or spark plug. Do you have any rodents running around there? Chewing up wires? Do you have a Durametric to pull any stored check engine lights (otherwise it's a guessing game).

Hmm, I am getting somewhat concerned. I bought one new coil pack, and started with the rearmost cylinder. Swapped out one by one, but did not get it to run right. So I proceeded with taking out the spark plugs. The first one on the left in the cars forward direction looked great, but the next two was wet and smelled badly from fuel: On this picture the fuel had already evaporated, but besides the fouling it looks ok to my untrained eye. It is Bosch FGR6KQE plugs in it, and looking at them they can well be the original plugs that came in the replacement engine 55 k miles ago. So, I will replace them, but then I don't know what to do next. Unfortunately I haven't bought the Durametric yet, so I can't give you the codes. When I add duty and shipping over here it almost get as expensive as the professional version, so cheap as I am it has to wait until I go to the US in March. So, does anyone know where to look next? Any cables that are prone to failing? Thanks, Johan

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Based on the info in your posts I believe the coils are suspect. They probably got damp from the damp weather. (I had my Boxster misfire after I left it sitting out (though covered) in climatic conditions that changed over a few days from mild and dry to cool and damp. In another case my Turbo misfired upon engine start after the car had sat out overnight in a pretty heavy rain.) There are no cables that can account for the behavior. That is by cables I assume you are referring to spark plug wires. The coil attaches directly to the plug. At the risk of adding confusion, but with the desire to be accurate, there is after some fashion some sort of a "cable" or plug "wire" between the coil proper and the plug but when (if) coils go bad the coil body is where the badness happens. This is the portion of the coil that is most exposed to the elements and suffers from this exposure. In the case of your car, that the CEL did not come on is a bit troubling. The CEL came on when my cars exhibited similar behavior and remained on. A read of the codes found several misfire codes. You can and should "test" the CEL: The CEL should come on when you turn the ignition key from the off position to the on position. The CEL should remain on until you start the engine then it should go out as the engine catches and begins to run. If the CEL doesn't come on when you turn the key to the on position you need to check the bulb. Even if the bulb is not working though a code reader can still tell you if the bulb (CEL) should be on and if it is what the error code(s) associated with the CEL are. And of course the codes can be erased too. If the CEL does come as it should when you turn the key from off to on and that fact it didn't come on when the incident happened this suggests the cause is not the coils (misfires) but perhaps the ignition switch or even bad (stale, very stale) gas. Or it could be the plugs. Or one or more fuel injectors is leaking. A code reader/data viewer can help you id the root cause of the behavior provided the root cause appears again. Sincerely, Macster.

The compelling issue is that both the P-car and the F-150 are fouling. I like Goldenwarrior's theory on bad fuel.

Hi guys, Thanks, I will replace the plugs today. I should clarify that the CEL is flashing when the engine is running rough from start. However, the CEL does not light up when the engine only is missing slightly at idle. Macster, reason I asked about the wires is that I recently replaced the AOS. I am afraid I damaged something in the process, or did something wrong then, since the same bank is the one running rough. Gonzo, I checked the fuel part, and it turns out I filled gas on two locations, several days apart. Regards, Johan

Very bad intake leaks can cause misfires. Since you replaced the AOS perhaps you might have a bad intake leak, and if that was the last thing you touched and it was running fine before. I wouldn't ever assume that a flashing CEL means misfires alone, the codes should be read out. Start with the simple stuff though, retrace your steps on the AOS, make sure there are no intake leaks. Change the plugs, inspect (or replace) the coils for cracks. Once you've gone over all that, now you get to move on to the bad stuff inside the engine... (some of which I mentioned above... broken spring, cracked cylinder wall, etc.) Perhaps a rat or mouse is living in your engine bay? Here is the misfire troubleshooting guide: http://www.renntech.org/forums/index...ttach_id=24613 A similar misfiring in one bank story here about someone who replaced their AOS and created a large intake leak after reassembling. http://www.renntech.org/forums/topic...r-engine-work/

The first thing I would check is if you have a miss on just a few cylinders or if it is running rough on all cylinders or if it is just one bank. I and most every tech I know won't do anything or make a guess to the problem until the codes and actual values are read. 9 times out of 10 the codes and actual values will give you a great place to start. At $300 the Durametric is a great investment.

+1 to above, we keep pounding that into his head, I think he has one on order.

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If you are afraid you damaged/upset something during the AOS replacement chances are high you did. When some anomalous engine behavior appears 'out of the blue' after some other work was done I always suspect the other work is at fault. While the AOS is probably ok (however, even a new one can be bad which is why there's a 2 year parts warranty on new Porsche parts) something happened during the AOS job. Rechecking everything related to the AOS and then checking any wires/connectors/lines not directly related but in the general vicinity is or should be high on your list of things to do. I'd be tempted to do the above checking *before* replacing any plugs or other hardware. Sincerely, Macster.

Thanks guys, Did a walk through of the AOS installation, but as far as I could see it looked ok. I need to get it on a lift to make sure. Then I changed all the plugs (a real PITA!) and swapped the coils from left to right. Started it, ran fine, and then it started to miss! On the other side.... So, since I was smart enough to put the one new coil on the rearmost right cylinder (which is the hardest one to reach), there are only two coils left to check. Since I didnt have any more strenght in the arms I decided to leave it until tomorrow. I am considering that there are two damaged coils, which could explain why I cant find out which one. Last time I drove it was the first time ever it ran in severe winter weather, meaning salty roads, heavy snow and rain. I am thinking the coils could have small heat cracks from south FL (there are no visible cracks on either coil) where water entered during my last run. Then the salt and moisture did their thing during the two days it was parked. Not ordered the Durametric yet, but I will do that for sure on my next trip to SFL. I'm living in a city where no shop has a durametric! Closest one is the dealership an hour away, so I really need to get one....

Are your gas tanks locked? I noticed before lubing my 996's filler lid that it wasn't locking sometimes. Just wondering if some lame kid put sugar or something in your tanks.

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If the missing followed the coils that's a good sign the coils are the cause. Those on the curb side of the engine get the worst of road splash and suffer the most degradation. If you have id'd 2 or 3 of 6 coils acting up and the coils are all about the same age -- going on what, 12 years old? -- I'd replace all 6 coils. About the time you get comfortable with the engine's better behavior and a big smug after replacing just 2 or 3 coils the engine will misfire again and you're back at the engine again replacing the other coils. Salt water is corrosive to be sure but another more subtle but real problem arising from salt water in this case is that the salt in the water when the water dries -- as it does when the engine is run and the coils heat up -- forms crystals and these crystals tend to expand the crack. Thus the crack widens and sooner than you think the coil's are really acting up. Sincerely, Macster.

Hi guys, thanks for your support. I replaced yet another coil, and now it is running as it should. I replaced it already on Friday, but when I was about to start the car, nothing happened! All lights where on, everything worked as it should, but not even a click from the starter solenoid. It has happened before, but then it started on the 10th try. No such luck now. I was prepared this might happen, since the ignition lock has locked up at below freezing temperatures. So I narrowed it quickly down to the ignition switch. After a 3 day bank holiday over here I could finally go today and pick up the $85 Audi switch (yes that is right, $85 for a $11 part in the US). It started right up and ran perfectly even though a crispy 10 degrees outside temp here today. So I hope this mean I can close this thread out, and finally be able to put 1000 miles on it before I can be sure the intermix was repaired by replacing the oil cooler. Thanks all! Johan

Sounds like it's time for a road trip!!!!

Yea Johan, so a coil pack fixed the rough idling, finally. Good luck on your next 1000 miles, hope it runs without a glitch for you.