Random Misfire Diagnosis
12-29-2004, 09:06 PM
#1
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Random Misfire Diagnosis
Using an OBDII tool today I read the codes that were causing a CEL. I got P0300, P0301, etc. Random Misfire. Yee Haaa!
So my first step, as a good Rennlister, was to search the archives. Lo and behold but what do I find: a posting speaking of blue sparks around the ignition components evident when the engine is observed running in darkness. I marched my butt down to the garage, eyeballed my beauty, started her up, raised the engine cover, dimmed the lights and what did I see? ...YEP! Blue sparks around both coils.
A response by Steve "PORSCHE EXPERT" Weiner to the original posting revealed that these coils should not show blue sparks. BAD COILS!!!
Mine are showing sparks at all four rivets and also show a greyish ash like substance on the coil of the body. Clearly I have a dielectric breakdown!!!
I'll be contacting Mr. Weiner tomorrow regarding coils.
I'm posting this as an FYI to anyone else experiencing similar issues.
Happy New Year!
Scott
So my first step, as a good Rennlister, was to search the archives. Lo and behold but what do I find: a posting speaking of blue sparks around the ignition components evident when the engine is observed running in darkness. I marched my butt down to the garage, eyeballed my beauty, started her up, raised the engine cover, dimmed the lights and what did I see? ...YEP! Blue sparks around both coils.
A response by Steve "PORSCHE EXPERT" Weiner to the original posting revealed that these coils should not show blue sparks. BAD COILS!!!
Mine are showing sparks at all four rivets and also show a greyish ash like substance on the coil of the body. Clearly I have a dielectric breakdown!!!
I'll be contacting Mr. Weiner tomorrow regarding coils.
I'm posting this as an FYI to anyone else experiencing similar issues.
Happy New Year!
Scott
12-29-2004, 09:14 PM
#3
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Scott. Great work. 
Steve is such a valuable resource to this board. I just wish I lived closer to him so I could take my car to him when it needed it. Maybe he'll open a Hawaii branch?
Steve is such a valuable resource to this board. I just wish I lived closer to him so I could take my car to him when it needed it. Maybe he'll open a Hawaii branch?
12-30-2004, 12:50 AM
#4
Rennlist Member
Where exactly did you see the blue sparks? I don't know what you mean by "coils".
Something similar happened to me this summer: I saw blue sparking between the king lead and the center lead on the top distributor. Visible in the dark. It turned out to be my own fault: I had hooked up a clip to that lead to run to my data logger to log RPMs, but when I removed the clip, the sparking stopped. Very weird and probably not helpful to you...
Something similar happened to me this summer: I saw blue sparking between the king lead and the center lead on the top distributor. Visible in the dark. It turned out to be my own fault: I had hooked up a clip to that lead to run to my data logger to log RPMs, but when I removed the clip, the sparking stopped. Very weird and probably not helpful to you...
12-30-2004, 01:51 AM
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Originally Posted by Jastx
Very cool road to discovery. Great to have resources like Steve on this board.
12-30-2004, 08:23 AM
#6
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Eric86Red911,
The coils I'm referring to are on my '96 993 with twin distributors. They're the ignition coils and are located on the aft wall of the engine compartment nearly directly across from the distributors.
The coils are each roughly the size of a pack of cigarettes (though I don't smoke
). Each side, left and right, top and bottom, has a rivet that holds a stack of metal plates together. It is at these rivets that blue arcing is evident and it is between the pair of rivets on each side that I'm seeing greyness in the rubber (signs of burning/charring of the rubber).
The arcing indicates a breakdown in the dielectric (insulation) of the coil itself. Arcing anywhere but at the spark plug is robbing the ignition process of that wonderful ignition/combustion thing which makes us go-fast! And we like to go fast!!!!
So I'm now shopping for the best price for a pair of ignition coils. Any suggestions????
Vrooom,
Scott
The coils I'm referring to are on my '96 993 with twin distributors. They're the ignition coils and are located on the aft wall of the engine compartment nearly directly across from the distributors.
The coils are each roughly the size of a pack of cigarettes (though I don't smoke
). Each side, left and right, top and bottom, has a rivet that holds a stack of metal plates together. It is at these rivets that blue arcing is evident and it is between the pair of rivets on each side that I'm seeing greyness in the rubber (signs of burning/charring of the rubber).The arcing indicates a breakdown in the dielectric (insulation) of the coil itself. Arcing anywhere but at the spark plug is robbing the ignition process of that wonderful ignition/combustion thing which makes us go-fast! And we like to go fast!!!!
So I'm now shopping for the best price for a pair of ignition coils. Any suggestions????
Vrooom,
Scott
01-02-2005, 01:33 AM
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Hi Scott,
I am getting the occasional misfire code as well and checked out my engine in the dark...I can see a very very faint light at some of the rivets on the coils. Its pretty faint but definitely there...but its not a bright spark or anything like that.
How bright were those sparks and have you chenged out the coils yet?
Cheers,
Mike
I am getting the occasional misfire code as well and checked out my engine in the dark...I can see a very very faint light at some of the rivets on the coils. Its pretty faint but definitely there...but its not a bright spark or anything like that.
How bright were those sparks and have you chenged out the coils yet?
Cheers,
Mike
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01-02-2005, 02:00 AM
#8
RL Technical Advisor
Mr. Scott:
FYI,...Porsche sells the coils as a pair only, on that steel mount.
These are a 993.602.071.00 and they run $ 217 for the pair.
Hope this helps: please let me know if I can be of assistance.
FYI,...Porsche sells the coils as a pair only, on that steel mount.
These are a 993.602.071.00 and they run $ 217 for the pair.
Hope this helps: please let me know if I can be of assistance.
01-02-2005, 07:16 AM
#9
Three Wheelin'
Originally Posted by campbesl
Eric86Red911,
The coils I'm referring to are on my '96 993 with twin distributors. They're the ignition coils and are located on the aft wall of the engine compartment nearly directly across from the distributors.
Scott
The coils I'm referring to are on my '96 993 with twin distributors. They're the ignition coils and are located on the aft wall of the engine compartment nearly directly across from the distributors.
Scott
01-02-2005, 11:17 AM
#10
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Thread Starter
Mike,
The sparks I observed were as you described - blue, fairly faint and at the rivets. Regardless of the faint nature, I don't think we should be seeing any such spark/arcing.
Scott
The sparks I observed were as you described - blue, fairly faint and at the rivets. Regardless of the faint nature, I don't think we should be seeing any such spark/arcing.
Scott
01-02-2005, 03:23 PM
#12
RL Technical Advisor
Greg:
Factory coils are it. There are no aftermarket solutions since these are impedance matched to the ECU's coil drivers.
FWIW,.....On the whole, these have been quite reliable and I can only remember replacing a few in the past few years.
Factory coils are it. There are no aftermarket solutions since these are impedance matched to the ECU's coil drivers.
FWIW,.....On the whole, these have been quite reliable and I can only remember replacing a few in the past few years.
01-02-2005, 09:11 PM
#14
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Had a similar experience with my car but it turned out to be the plug wires.
The insulation had broken down through the years. Man, those things are expensive..+/- $500
mike
The insulation had broken down through the years. Man, those things are expensive..+/- $500
mike
01-03-2005, 02:09 AM
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Thanks Scott,
Please post when you have installed the new coils to see if the misfire has gone away...that would be great!
Anyone else with a healthy 993 willing to see if their coils have any glowing or sparks in the dark?
I would hate to replace the coils and find out that it was a waste of $$$... ;-(
Cheers,
Mike
Please post when you have installed the new coils to see if the misfire has gone away...that would be great!
Anyone else with a healthy 993 willing to see if their coils have any glowing or sparks in the dark?
I would hate to replace the coils and find out that it was a waste of $$$... ;-(
Cheers,
Mike