Spark plug diagnosis needed... -

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post #1 of 7 Old 02-14-2003, 10:29 AM Thread Starter
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1992 YJ Wrangler 
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Spark plug diagnosis needed...

hey guys i pulled my plugs the other day and they looked like they have been too hot. I looked in my Haynes manual and i could really match it to anything but that was the closest idea i could come too. I don't have them with me but I can describe them better later. My question is what can i do to adjust the engine so its not running hot?

o and heres some specs
4.0 in a '92 with a ton of miles (over 200,000)
rear main seal is leaking but not bad
just replaced the water pump about 4 months ago
the temp guage never reads hotter than normal
and the plugs i took out were Bosch 2s and replaced with Bosch 4s
plug wires are el cheapo
ummm... let me know what you guys think is up. thanks for the help in advance

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post #2 of 7 Old 02-15-2003, 09:18 PM
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You could upgrade to a 3core aluminum radiator (GDI at, drop in a 180 thermostat, put in an electric fan or look into checking if your clutch on the factory fan is still working right.

Would be a good time to replace the water pump as well.

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post #3 of 7 Old 02-16-2003, 08:48 AM
Swamp Boy
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I could be wrong but when the chiltons says the plug is to hot I think they are refering to the voltage not the temperature..
Check your air fuel mixture(may be to lean) also check for vacum leaks .. I think the manuel says your valves could be sticking as well..However you can buy colder plugs not sure what thay would be ..Good luck..

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post #4 of 7 Old 02-16-2003, 09:11 AM
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Hot or cold plugs are a reference to the plugs ability to conduct heat. Hotter plugs have a longer ceramic tip than colder plugs. This increase in insulation (ceramic) keeps the tip of the plug hotter. Hotter plugs are generally better at burning away oil deposits than colder plugs. Ever see a spark plug spacer for badly smoking engines? It's a ring that screws into the cylinder head, then the plug screws into the spacer. The extra insulating characteristics of the spacer allow the plug to run hot enough to fire in an oily mist. If your plugs are too hot, then you can go a range or two colder at the risk of having the the plugs foul up. I would stay with the manufacturers recommended plug. Any abnormal plug wear is probably an indicator of faulty combustion.. ie too rich (black sooty) , too lean (white chalky), detonation (broken insulators, white, salt and pepper look).

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post #5 of 7 Old 02-17-2003, 06:45 PM
wrangler john
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You may wish to have someone perform an injector flow test to make sure the injectors are working properly. Are all the plugs looking the same or is it just one? if thats the case I would take a good look at the injectors. If it is all cylinders you may want to check your fuel pressure. Im not sure what the spec is but that could be a concern as well.

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post #6 of 7 Old 02-18-2003, 08:33 PM Thread Starter
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well they are all the same. I guess it needs to be looked at by a real mechanic... hmm. I got to get the brakes done soon anyway, i might as well do that then too. ok thanks guys
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post #7 of 7 Old 02-19-2003, 08:28 PM Thread Starter
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well i'm a moron... the plugs were normal. showed the mechanic and he was like... nope, nothing wrong just normal wear. But he was cool and didn't make me feel stupid. Plus he showed me how to replace my brake pads as well. Real cool/professional shop, I'll definately be going back there again.

o well, I guess we all started out clueless huh? anyway theres the scoop, thanks for the help.
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