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2000 Porsche 996 coupe

120k 6spd

I need some help figuring this one out. At idle and normal daily driving I do not have not have any issues but when I down shift and have it WOT I get a cylinder #6 misfire when I reach 5K RPM. Here is a little more information:

misfire only in #6 at about 5 or 5.5K for the past 6 months

1) New coils 1.5 years ago

2) Changed Spark plugs over the weekend and inspected coils for cracks they were not any cracks in the coils the spark plugs showed normal wear

3) Durametric codes: I cleared the codes and this is the only codes that keep popping up

P0300 Porsche fault code 507 - Misfire detection (total)P0306 Porsche fault code 509 - Misfire cylinder 6

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2000 Porsche 996 coupe

120k 6spd

I need some help figuring this one out. At idle and normal daily driving I do not have not have any issues but when I down shift and have it WOT I get a cylinder #6 misfire when I reach 5K RPM. Here is a little more information:

misfire only in #6 at about 5 or 5.5K for the past 6 months

1) New coils 1.5 years ago

2) Changed Spark plugs over the weekend and inspected coils for cracks they were not any cracks in the coils the spark plugs showed normal wear

3) Durametric codes: I cleared the codes and this is the only codes that keep popping up

P0300 Porsche fault code 507 - Misfire detection (total)P0306 Porsche fault code 509 - Misfire cylinder 6

Could be any number of things; you could still have a coil breaking down under load, which could be eliminated by swapping with another coil and checking to see if the misfire moves with the coil. Bad injector would do the same thing, and could also be isolated by swapping test. You could have a bad valve spring on that cylinder that is hanging a valve open at high RPM. Afraid this is going to require some more digging and using the process of elimination to narrow down the problem.

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Thanks for the quick reply. I swapped the coils in #6 and #5 yesterday and I'm still getting the same misfire on #6 today. So I'm guessing the coil is not the problem. some additional info that I have noticed.

1. I know the exhaust system crosses over, so the driver's side exhaust comes from the passenger side. What I have noticed is that the exhaust coming out of the drivers side tip is not as strong as the passenger side tip.

2. At the higher RPM the engine revs fine except for the stutter (misfire) at around 5.5K RPM and there seems to be a drop in power after about 5K RPM.

I noticed that when using the durametric that I do not have any cam degree deviation it consistently says zero degrees. Shouldn't the value change when reving.

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Could also be a lifter problem

And also do the compression and leak down numbers show OK? I noticed you mention plugs show normal wear, so just asking.

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I do not have the tools to do a compression test. Today on the drive home I will log some data on my durametric and I will upload it this afternoon. What I don't know is what values I should check to help better narrow my problem down.

I did a quick test of the cam adjustment at idle with durametric. When testing the engine ran a little rougher when I tested both sides individually and returned to normal when I stopped the test. So I'm assuming that the cam adjustment is working fine.

Would a bad catalytic converter explain the lack of exhaust flow coming from the passengers side?

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I do not have the tools to do a compression test. Today on the drive home I will log some data on my durametric and I will upload it this afternoon. What I don't know is what values I should check to help better narrow my problem down.

I did a quick test of the cam adjustment at idle with durametric. When testing the engine ran a little rougher when I tested both sides individually and returned to normal when I stopped the test. So I'm assuming that the cam adjustment is working fine.

Would a bad catalytic converter explain the lack of exhaust flow coming from the passengers side?

No, because it would effect all cylinders on that bank, not just the one. A bad cat would also throw codes.

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Thanks. that's what I thought

I do not have the tools to do a compression test. Today on the drive home I will log some data on my durametric and I will upload it this afternoon. What I don't know is what values I should check to help better narrow my problem down.

I did a quick test of the cam adjustment at idle with durametric. When testing the engine ran a little rougher when I tested both sides individually and returned to normal when I stopped the test. So I'm assuming that the cam adjustment is working fine.

Would a bad catalytic converter explain the lack of exhaust flow coming from the passengers side?

No, because it would effect all cylinders on that bank, not just the one. A bad cat would also throw codes.

Thanks that what I figured. do you have any suggestions on which values I should log on my drive home? I figured that I would get:

1. cam deviation

2. Range 2 Cylinder 4-6(FRA2)

3. Range 1 Cylinder 4-6(TRA2)

4. Injection time

5. RPM

6. ??

7. ??

8. ??

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have you pulled the plug on #6? If it looks ok, swap with with #5

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have you pulled the plug on #6? If it looks ok, swap with with #5

I changed all the plugs out over the weekend and im still having the same issues

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have you pulled the plug on #6? If it looks ok, swap with with #5

Today I will change out the new spark plug in #6 and put back in one of my old plugs and see if there is a change. Could a plug on be only affect at higher RPMs when under load?

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I just wanted to add that yesterday my car was difficult to start after sitting for about 3 hrs after lunch. The engine turned over and I had to do a lot of cranking but it eventually started and I smelled fuel.

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have you pulled the plug on #6? If it looks ok, swap with with #5

Today I will change out the new spark plug in #6 and put back in one of my old plugs and see if there is a change. Could a plug on be only affect at higher RPMs when under load?

Yes, a single plug or coil pack can break down under load.

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have you pulled the plug on #6? If it looks ok, swap with with #5

Today I will change out the new spark plug in #6 and put back in one of my old plugs and see if there is a change. Could a plug on be only affect at higher RPMs when under load?

Yes, a single plug or coil pack can break down under load.

Thanks. I will change out the plug and post an update this evening

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Hey guys just an update. I replaced #6 plug with a new Beru plug but wasn't able to go for a drive to check it out cause my belt shredded because of an bad idler pulley. I just got back in town and got my car running again. I also added some techron. About to take it out for a test drive and see if it registers the same codes.

Edited by wesley_817

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ok.. so I am still getting the same code after putting in a new spark plug and switching around the coil packs. So I have determined that it is not the spark plug or coil pack. I am gonna try to reset the computer by disconnecting the battery for awhile.

1) What I have noticed is that once I get the check engine light my car idles and drives rough. If I run my durametric while the car is idling rough and clear the code then the idle immediately smooths out.

2) I have also noticed that the exhaust originating from the passenger side is not as strong as the opposite side. (maybe time for a new cat)

3) Also I started to hear the fuel purge from the gas tank when I turn off the engine.

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It could be a variocam actuator problem.

Did you check compression in #6 versus other cylinders.

Did you try swapping injectors between cylinders?

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It could be a variocam actuator problem.

Did you check compression in #6 versus other cylinders.

Did you try swapping injectors between cylinders?

i have not checked the compression in #6 yet. Is there an easy way top check the variocam? swapping the injectors was next on my list.

what is your thought s on the car is idling rough and when i clear the code the idle immediately smooths out.

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That's likely due to the fuel-trim reset. Most likely it will revert back to rough idle if you leave it idling long enough to re-learn the fuel trim.

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That's likely due to the fuel-trim reset. Most likely it will revert back to rough idle if you leave it idling long enough to re-learn the fuel trim.

I will have to look into this, but so far I only sometimes get the rough idle with the check engine light. I only get a check engine light if I have it wide open around 5.5K. Otherwise I will never get a check engine light or any codes (I have driven it normally for weeks and no check engine light or code). When I do get the rough idle with check engine light it is remedied by clearing the check engine light or by turning the car off and restarting it.

Tomorrow I will check the:

- Adaptation value, area 2, cylinders 1 - 3 (FRA)- Adaptation value, area 2, cylinders 4 - 6 (FRA2)- Adaptation value, area I, cylinders 1 - 3 (TRA)- Adaptation value, area I, cylinders 4 - 6 (TRA2)

does anyone know the normal value ranges for these?

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I hate to say this but if you ruled out an electrical misfire and fuel misfire, that only leaves: a compression misfire. You really need to do the suggested compression test. The equipment is not expensive and performing the test is not hard. Can you post a photo of #6 plug?

All you need is a helper, remove all plugs, kill power to coils, remove air cleaner, manually keep intake butterfly wide open, crank engine sufficient number of times for each cylinder, record and compare results. Nothing to it.

Edited by krazyk

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I hate to say this but if you ruled out an electrical misfire and fuel misfire, that only leaves: a compression misfire. You really need to do the suggested compression test. The equipment is not expensive and performing the test is not hard. Can you post a photo of #6 plug?

All you need is a helper, remove all plugs, kill power to coils, remove air cleaner, manually keep intake butterfly wide open, crank engine sufficient number of times for each cylinder, record and compare results. Nothing to it.

I haven't ruled out a fuel misfire yet, but i believe that i have ruled out electrical misfire. I plan on doing the compression test on Wednesday or Thursday. Do i really need to remove all the plugs or can i just disconnect the coils on 1-5 and then just take out the plug on #6 for the compression test?

I will take out plug #5 and #6 tomorrow and post up a pic to show a comparison

Edited by wesley_817

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Have you done a fuel pressure test? Although if it is only happening on number 6 I would be surprised if it is pressure related.

Going back to Ahsai's post, when you reset codes on your MY 2000 car it should reset trims. I would focus on this, and if it were me swapping injectors would be next on my list (and compression check).

http://www.renntech.org/forums/topic/31772-compression-test-diy

The only other idea is that somehow resetting codes has something to do with variocam actuation. I've seen some strange things when a DME goes bad, and perhaps that is related. Although bad variocam should throw random misfires on the entire bank.... but I have seen bad variocam not throw misfires, so perhaps you just have a co-related problem with #6. The reason being you said rough idle... fuel trims would need to be really out of whack for that to happen.

Have you read out your fuel trims (FRA/TRA) and compared them with the setpoints? (WHEN the problem is happening or engine is running rough or has 30+ miles on battery reset)

http://www.renntech.org/forums/topic/38219-acceptable-rough-running-values/#entry202255

Edited by logray

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Not sure this helps but.....I believe that at roughly 5,000 rpm the variocam returns to non advance .This could be simply a coincidence but I don't think so .If the car idles normally and runs fine until that threshold it could be a culprit .Not knowing how the dme is programmed it's hard to say why the rest of the bank doesn't show misfires .

Just a thought...........

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ok guys sorry for the late reply.. over this weekend I investigated my exhaust problem where the right exhaust tip was producing about 40% compared to the left exhaust. after removing the muffler I noticed that part of my CAT was lodged behind my O2 sensor. I replaced my Cat and now it runs like a champ again. Thanks for all of your quick responses.

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