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So i was driving home today from work, and all of a sudden it stumbled, then would not maintain speed.....press gas more and it just sputters......so i coast it out as far as i could.

Try driving it slightly to get into a parking lot and it sputters and shakes hard.....definitely not driveable.

Got towed home and pulled the coilpacks and plugs.....the car idles semi ok, and after it cooled down a bit seemed to be "better"

None of the coil packs have cracks.....plugs were all gas soaked. coilpacks are all .04 revisions.

Questions:

1. Is this a typical coilpack failure....just all of a sudden multiple misfires and unable to continue to drive?

No, not unable to drive

2. will a few failed coils end up soaking all plugs at some point, or did i somehow fail all coilpacks at once?

No, only the cylinders that are missing should show signs of running cold

3. Do they always crack when failed, or can they fail without being cracked....None of mine seem cracked.

Yes, they don't need to be cracked to have failed, or starting to fail.

Thanks. I have almost 100k on those coils, so i felt like i was running on borrowed time, so it seems logical.

SOLVED: It was the driver side fuel pump. Looks for the DIY

Edited by clarksongli
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i guess one of the big questions would be can a coil fail without cracking?

I'll check the fuses, but since none of the coils have shorted to the head, i would assume the fuses would be ok.

I suppose it could be a fuel pump, although i know i was running pig rich, which i assumed was failed spark? the cats were screaming hot, and plugs were wet....i would guess a failed fuel pump would do the opposite? Run Lean?

My 04 S acted that way, turned out cracked cylinder #3 wall. No idiot lights or anything. Ended up with large paperweight :cursing:

Hopefully this isn't the case....my thought it isn't since sometimes it would run clean....but only for short periods of time.

Edited by clarksongli
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  • Moderators

i guess one of the big questions would be can a coil fail without cracking?

I'll check the fuses, but since none of the coils have shorted to the head, i would assume the fuses would be ok.

I suppose it could be a fuel pump, although i know i was running pig rich, which i assumed was failed spark? the cats were screaming hot, and plugs were wet....i would guess a failed fuel pump would do the opposite? Run Lean?

My 04 S acted that way, turned out cracked cylinder #3 wall. No idiot lights or anything. Ended up with large paperweight :cursing:

Hopefully this isn't the case....my thought it isn't since sometimes it would run clean....but only for short periods of time.

Don't expect to find a bad coil with cracks or other outwards signs of problems. We get cars in all the time with misfires that trace to the coil packs; when extracted, the coil packs look fine, they just don't work properly. Nature of the beast.....

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Don't expect to find a bad coil with cracks or other outwards signs of problems. We get cars in all the time with misfires that trace to the coil packs; when extracted, the coil packs look fine, they just don't work properly. Nature of the beast.....

Thanks! that clears up one concern of mine! JFP, do you see situations where several coils fail causing BOTH near undriveable condition as well as wet plugs in all cylinders?

I guess the other thing i should mention is i only drove the car maybe 200 ft before checking the plugs.....maybe it didn't run long enough and the plugs were all wet simply because it only ran for 30 seconds?

Edited by clarksongli
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Don't expect to find a bad coil with cracks or other outwards signs of problems. We get cars in all the time with misfires that trace to the coil packs; when extracted, the coil packs look fine, they just don't work properly. Nature of the beast.....

Thanks! that clears up one concern of mine! JFP, do you see situations where several coils fail causing BOTH near undriveable condition as well as wet plugs in all cylinders?

I guess the other thing i should mention is i only drove the car maybe 200 ft before checking the plugs.....maybe it didn't run long enough and the plugs were all wet simply because it only ran for 30 seconds?

Coils generally fail individually, but because of the general difficulty in getting at them on some models (like the 996 Turbo cars), owners often opt to swap them all out just because they do not want to revisit the problem next week.

In your case, you may not have allowed the car to get up to temp, resulting in wet plugs.

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I suppose it could be a fuel pump, although i know i was running pig rich, which i assumed was failed spark? the cats were screaming hot, and plugs were wet....i would guess a failed fuel pump would do the opposite? Run Lean?

I cannot comment on coil pack issues as in around 100k miles of Cayenne (3 cars) ownership I have never had a spark related problem. However what you describe in the first two lines of your first post is identical to what I experienced when one of my fuel pumps failed. The car may run normally again after switching off and restarting.

With regards to the rich issue, a number of people have reported improved fuel economy after fuel pump replacement.

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Check my post below about multiple misfires. Mine was apparently caused by split insulation on one of the coil packs which shorted out the whole bank. My car also has 100,000 miles and my cure was to remove the tape insulation and repair the damaged wires. I suspect prolonged heat caused the insulation to become brittle. The car runs fine now

Steve

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I suppose it could be a fuel pump, although i know i was running pig rich, which i assumed was failed spark? the cats were screaming hot, and plugs were wet....i would guess a failed fuel pump would do the opposite? Run Lean?

I cannot comment on coil pack issues as in around 100k miles of Cayenne (3 cars) ownership I have never had a spark related problem. However what you describe in the first two lines of your first post is identical to what I experienced when one of my fuel pumps failed. The car may run normally again after switching off and restarting.

With regards to the rich issue, a number of people have reported improved fuel economy after fuel pump replacement.

So i am shocked...but i pulled the codes.....had a few fuel low pressure ones.....

did the fuse trick to isolate which pump....pull #14 and the car runs fine....so driver side pump is bad i believe?

Edited by clarksongli
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Good to here.

Did you change both pumps?

No actually i talked with both suncoast Porsche as well as my friends father, who is the Porsche Master Mechanic for a large NY shop, they both said to replace just the one. So we will see, but i've worked with my friends father before, and i trust him for sure.....he has won the annual porsche tech challenge many times, so i don't doubt his experience and knowledge.

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