Reading a spark plug????

Can some one help me out with this. What would cause a plug to do this. Needless to say it is running like @$$

Is that coolant on there? Is your junk overheating? Might be a crack in the head or a bad head gasket causing coolant to get in the combustion chanber.

bosch.. ugh

Does it have a greenish tinge to it?

No greenish tinge, never overheats. I don't remember putting in the Bosch plugs, but I guess I must have. I usually use Champions.

Yeah its the bosch plug. A 4.0 isnt designed for a plat plug, its burns too hot. f its white its running to lean, if its black its running too rich.

Bosch plugs belong in VW's, Volvos, Saab and the like. That plug still has a lot of deposit on it. I would throw a fresh set in correctly gapped and pull that cylinder every couple days to monitor it...

A plug that f***** up cant really be read,get some new ones and start over!

Dragline said:

Can some one help me out with this. What would cause a plug to do this. Needless to say it is running like @$$

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Hey, I saw your post over on JF about this, and was curious if those plugs had actually been in there for 80,000 miles. If those are standard copper plugs, that's 50-60,000 miles more than they're typically good for.

As for running lean: with plugs in that condition it makes sense. They're so gummed-up that you're going to get incomplete combustion (which the oxygen sensors will detect as unburnt fuel), causing the computer to lean out fuel delivery. If you're lucky, your catalytic converter hasn't bit the dust from raw fuel ending up in it as well...

thats coolant probably coolant. u may be looking at a cracked head.

serialphreak said:

thats coolant probably coolant. u may be looking at a cracked head.

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doesn't coolant clean the plug real well? that looks like ash to me from running lean.

just throw a set of champions in it and post in the morning!

x99j said:

doesn't coolant clean the plug real well? that looks like ash to me from running lean.

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looks like conductive corrosion. but thats just my opinion

Replace them all and do a compression test.

First off, that doesn't look like the right plug for a 4.0L but that isn't your problem. The buildup on the plug is not the plugs fault, you have something else going on.

You have a combination of things causing your buildup problem. Buildup can be caused by several different things. The most common are oil, leaking antifreeze, fuel additives, or bad gas. Oil tends to cause brownish buildup, but not always. If you are running lean, but are burnig oil, you will end up with a white buildup. Are you getting any ping? This would lead me to think you are running too lean and burning oil, otherwise my bet is on a leaky head gasket and you are burning antifreeze.

Back to the type of plug. Did you buy this vehicle used? The plug you have looks like a higher heat range than stock. This is a common trick on a vehicle that is burning oil, to keep it from fouling long enough to sell the vehicle.

I was wrong. I recalculated and they have ONLY been in there 60K miles. I think you guys may be reading too much into this. Remember they are Bosch Platinum and they have been in there 60K miles. I don't think it's coolant, I just think it's ash buildup. My PCV hose was practically non existant and I have a cracked exhaust manifold (big shocker there huh).

casm said:

As for running lean: with plugs in that condition it makes sense. They're so gummed-up that you're going to get incomplete combustion (which the oxygen sensors will detect as unburnt fuel), causing the computer to lean out fuel delivery. If you're lucky, your catalytic converter hasn't bit the dust from raw fuel ending up in it as well...

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I'm almost certain the cat is fried. That's what started me checking plugs. All of a sudden it started running poorly and the cat was getting so hot it was glowing red and the floorboards started to smoke. I took it to a shop to get the cat replaced assuming it was plugged and that's what was making it run so bad. The shop wouldn't replace the cat until they were sure there was not something else making the engine run so poorly. Anyway I have replaced all 6 plugs with Champions, replaced the PCV hose, "modified" the exhaust so the blocked cat is not so restrictive and it runs like a champ now. I'm going to pull the plugs ever week or so and check thier condition. I'll go and get the cat replaced next week. As for the cracked manifold. it will have to wait. It's been cracked for years but has just recently gotten worse. As for the plugs here is a picture of the rest of the family:


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old_man said:

Back to the type of plug. Did you buy this vehicle used? The plug you have looks like a higher heat range than stock. This is a common trick on a vehicle that is burning oil, to keep it from fouling long enough to sell the vehicle.

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I bought the vehicle new 14 years ago. I have no idea why I used Bosch Platinum plugs. It was a while ago when I put them in.

Everyone has their opinions, I have mine. MY rig runs great on Bosch Platinum +4's. To me, it has more power than when I used Dealer Champs.

That plug with a missing tip is a sure sign of pre ignition.

I'll have to admit, up until last week mine ran great on Bosch Platinums. I just kept them in for too long.

Reminds me of a quote by Mickey Mantle:

If I knew I was going to live this long, I'd have taken better care of myself.

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old_man said:

That plug with a missing tip is a sure sign of pre ignition.

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What should I look for causing pre ignition

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