put new plugs in after aprox 100 miles plugs on the left are burnt fried caked black and the plugs on right are brand new..how can this be?


Asked by Aug 10, 2015 at 11:45 PM about the 1993 Ford Ranger

Question type: Maintenance & Repair

what could cause this?  truck runs good but wont start after it warms up until the motor
cools then fires right up..at stops  idle speeds up

4 Answers


You may be burning lean, did you change the coil packs, is your timing correct?


Sounds like left bank could be running lean. Maybe a vacuum leak, gasket, etc. You might want to bite the bullet and put in platinum plugs. They pay for themselves in time.


Why did you replace the plugs to begin with, were they too burnt? Need more info to diagnose this. A vacuum check would be advised although I doubt that is it. Also do not wait 100 mi., put in a new set of plugs do a power run then pull and read them immediately. Have you checked for codes?


I might have read your heading wrong... are the left bank plugs black and wet? what do you mean by caked? That would indicate oil and the right bank is burning properly.

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