Changed all my plugs out at 43k. Found two bad plugs!!! What caused it??? The bad plug fairy! Who knows!! I think bad plugs are usually caused by an engine running too rich. But then you would also think that all of the plugs would go bad. I don't know. Maybe Ford put in two duds at the factory!! If you find out anymore, please post. I too would like to know why I had 2 bad plugs.

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97F150 XLT SC 4x4 Flairside 4.6 V8 5sp Dk Toreador Red, 3.55LS
ARE tonneau cover, p255/70rx16 tires (came w/235), Superchip
Pioneer CD w/4 Polk Speakers & Clarion APA5240amp, skid plates
bed liner, side window deflectors, reese hitch, K&N air filter
40s-2chamber Flowmaster, Bosch +4 spark plugs, rustproofing
Better Built Stainless nerf bars

 

Lots of things can cause plugs to go bad....cracks in the porcelain insulator, fouling [too rich, oil , etc]... another reason some might go bad before others, is that they are mass produced, and try as we might, not every mass-produced product is identical when comparing two or more supposedly- identical items.

[This message has been edited by Jerry D (edited 07-22-1999).]

 

The other night my check engine light came on and remained steady while cruising. After several restarts and a fresh tank of gas it remained on. After having it serviced I was advised the #5 plug was replaced as it was missing though there were no apparent driveability problems. What would cause this?

98 F150 XLT SC 4X4/ 4.6/Auto Trans

[This message has been edited by grege (edited 07-21-1999).]