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Pulled this out of a 94 jeep 4.0L in line 6. This is a new one to me I have never see a plug fail like this in the last 60 years?

Any one have any theories?



 

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Severe detonation (pinging) that cylinder is running extremely lean. I would look for a air/fuel mixture problem. A vacuum leak, A defect in the EGR system. Maybe the ports in the head for the EGR are all plugged with carbon except this cylinder? That would pull all EGr from that one cylinder and cause a problem like that. You should get a video scope and see if the top of the piston is damaged.
 

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Discussion Starter #3
Severe detonation (pinging) that cylinder is running extremely lean. I would look for a air/fuel mixture problem. A vacuum leak, A defect in the EGR system. Maybe the ports in the head for the EGR are all plugged with carbon except this cylinder? That would pull all EGr from that one cylinder and cause a problem like that. You should get a video scope and see if the top of the piston is damaged.
Pulled the head every thing is good???
 

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What cylinder is it? Any vacuum devices off that runner on the intake? PCV valve, brake booster, EGR? Did the engine run ok before this? Leaking intake gasket? Sure seems like the cause would be severe heat or lean mixture. Hmmm got me thinking.
 

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a bad injector or a vacuum leak might be the cause of the lean f/a mix but it may have been a defective plug that looks like a mechanical failure on the ground electrode not a a heat induced failure, pre-ignition and detonation(not the same things) can cause the ground electrode to melt but the porcelain and plug color tends to look a bit different if thats the case


http://forum.grumpysperformance.com/viewtopic.php?f=44&t=937&p=6449&hilit=+detonation#p6449

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=202
 

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Discussion Starter #6
a bad injector or a vacuum leak might be the cause of the lean f/a mix but it may have been a defective plug that looks like a mechanical failure on the ground electrode not a a heat induced failure, pre-ignition and detonation(not the same things) can cause the ground electrode to melt but the porcelain and plug color tends to look a bit different if thats the case


http://forum.grumpysperformance.com/viewtopic.php?f=44&t=937&p=6449&hilit=+detonation#p6449

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=202
Glad to hear some one else say that. the thought crossed my mind that it may have been a defective plug. Be cause nothing else indicated heat or pre-ignition.
 
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