This is topic Normal Spark Plug Wear? (Pic) in forum Tech Talk at Northern California Ford Owners  .


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Posted by fredfifty (Member # 10320) on :
 
I have a SES light on my 99 Tahoe (142k mi) and it reads P0304 misfire cylinder 4. I pulled the plug out (see pic) and to me it looks normally worn, however the gap was about .70 when it should have been .60

I regapped and installed but it still misfires. Im thinking a full tuneup is in order? What do you think.


 

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Posted by hurting your feelings (Member # 13641) on :
 
Move the spark plug to a different cylinder if mis-fire follows to that cylinder the plug is the problem. An you have a vortec engine an the have a big problem with there fuel injector's an the spider that feeds them.
 

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Posted by fredfifty (Member # 10320) on :
 
Ive been reading about that spider injection problem...its a 300 dollar part so i hope its not that. So the plug looks normally worn though? I will get or swap spark plugs tmmrw and test it, thanks...
 

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Posted by hurting your feelings (Member # 13641) on :
 
Looks to be wet in the picture. I would have to see a better picture on the plug.
 

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Posted by fredfifty (Member # 10320) on :
 
When i pulled the plug out, thats the first thing i looked for, wetness. But it was dry but it had a stale burnt smell if that makes sense.
 

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Posted by fredfifty (Member # 10320) on :
 
Better pic i hope


I bought a new ac delco plug, gapped it to .060 per specs and installed in #4 cylinder. Idles better, no obvious misfire when i give it some gas. So i cleared the code, let it run for a couple minutes and no SES light.

I hope that was it...now a full tune up.

[ 2014-11-12, 09:13 PM: Message edited by: fredfifty ]
 

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Posted by fredfifty (Member # 10320) on :
 
Dp

[ 2014-11-12, 09:13 PM: Message edited by: fredfifty ]
 

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Posted by hurting your feelings (Member # 13641) on :
 
Plug does look to be worn.I would give a couple days of drive after replacing that plug just to make sure the mis-fire has gone away.
 

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Posted by Tom Renzo (Member # 13165) on :
 
You did the right thing by replacing the plug and clearing codes to test it. But the gap is a little wide. We run them at .042-.045 max

[ 2014-11-13, 04:13 AM: Message edited by: Tom Renzo ]
 

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Posted by fredfifty (Member # 10320) on :
 
What are the pros and cons of .060 and .042? Im just gapping the plugs based off the factory specs, but if it benefits me more to narrow the gap ill do it.

Thanks
 

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Posted by hurting your feelings (Member # 13641) on :
 

quote:

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Originally posted by fredfifty:
What are the pros and cons of .060 and .042? Im just gapping the plugs based off the factory specs, but if it benefits me more to narrow the gap ill do it.

Thanks

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quote:

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Originally posted by fredfifty:
I dont drive it much now, but i will when i know the misfire is gone. Curious on the .042 gap though, is it for more power?

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quote:

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Originally posted by Tom Renzo:
I build many chevy engines in my shop and we have found that a closer gap works much better. Reducing the gap will make it more reliable. As the matter of fact Chevy had a service bulletin on reduced plug gaps. With that the stock gap according to GM is .050-.060 All data says .060 as posted in the vehicles in car emission decal.

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