Strange deposits on only one plug?
Thread Starter
Instructor
Joined: Jun 2008
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From: NY
Strange deposits on only one plug?
Guys,
I pulled my plugs last night, and one of them has some strange deposits on it. Looks like a dark ash material that's mostly on the ground strap, but the porcelin is a little darker too. It dosent seem to resemble detonation, and the rest of the plugs look perfect. Compression check was good on all cylinders and the AF ratio is in the low 11's. A plug chart that I found said it's contamination from the oil or fuel additites, but i'd think that i would see that on the rest of the plugs too. Any ideas? Again I've seen detonated plugs before (damaged, pepper deposits) and this dosent look like that.
Travis
EDIT-the material is pretty baked on, won't scrape off, or at least very easily. I changed that plug to a different cylinder and I'm going to check them again. This is on the 3rd cylinder back on the drivers side (not good with chevy numbers yet heh)
I pulled my plugs last night, and one of them has some strange deposits on it. Looks like a dark ash material that's mostly on the ground strap, but the porcelin is a little darker too. It dosent seem to resemble detonation, and the rest of the plugs look perfect. Compression check was good on all cylinders and the AF ratio is in the low 11's. A plug chart that I found said it's contamination from the oil or fuel additites, but i'd think that i would see that on the rest of the plugs too. Any ideas? Again I've seen detonated plugs before (damaged, pepper deposits) and this dosent look like that.
Travis
EDIT-the material is pretty baked on, won't scrape off, or at least very easily. I changed that plug to a different cylinder and I'm going to check them again. This is on the 3rd cylinder back on the drivers side (not good with chevy numbers yet heh)
Thread Starter
Instructor
Joined: Jun 2008
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From: NY
Thread Starter
Instructor
Joined: Jun 2008
Posts: 209
Likes: 1
From: NY
Actually, the best way that I can describe the deposits would be similar to carbon deposits that you'd find on the back of an intake valve. I tried to take a pic but i couldent get a good one.
Melting Slicks
Joined: May 2002
Posts: 3,210
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was it wet at all? I think you're talking about cylinder 5. if you wanted to you could put some fresh plugs in, do a pull to redline, keep your foot on the gas, and shut the car off to read the plugs. its best to do this at a track obviously, and carry an extra set of plugs with you to throw in after you pull yours and take them back to the pits to read them.
or, if it wasn't missing at all like you said, you could keep driving the car and not worry about it...
or, if it wasn't missing at all like you said, you could keep driving the car and not worry about it...
Thread Starter
Instructor
Joined: Jun 2008
Posts: 209
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From: NY
Anti seize was on the threads, but i put it on all the threads. I don't think its material from scraping the threads because it won't easily come off, also the porcelien is darker then the rest of the plugs.
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Thread Starter
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From: NY
I'll do my best when i get back into town. Also, what would cause only one cylinder to do this? The only thing it could be to me is an injector....but they only have 5K on them and the fuel filter is just as fresh. I honestly don't think that it's a 'problem", but i am curious as to why it's like that. The AF ratio at WOT is low 11s..
Le Mans Master
Joined: Oct 2003
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From: PA
St. Jude Donor '08
I'll do my best when i get back into town. Also, what would cause only one cylinder to do this? The only thing it could be to me is an injector....but they only have 5K on them and the fuel filter is just as fresh. I honestly don't think that it's a 'problem", but i am curious as to why it's like that. The AF ratio at WOT is low 11s..
can be a multiple of things....no need to start guessing..diagnose is key
Thread Starter
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From: NY
What cylinder in these cars seems to run the leanest/hottest/get damaged first? I was thinking too that if it was a clogged injector, that the plug would show signs of being lean, not dark carbon like deposits...
Le Mans Master
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From: PA
St. Jude Donor '08
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From: NY
Thread Starter
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From: NY
clyinder 5 is the one in question. When it's one cylinder, that limits it down alot i'd think, to an injector or ignition...(assuming the timing/tuning is set the same to that cylinder)
Le Mans Master
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St. Jude Donor '13
Steve
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From: NY