<HR style="COLOR: #666666" SIZE=1><!-- / icon and title --><!-- message -->My 97 F-150 misfires at 40-50 mph, and/or going up hill. Have replace plugs, ignition wires. Works for awhile then returns. Noticed burned marks on plugs from electrode to base along ceramic and rust color around plug boots. Replaced plugs works for awhile then plug failure reappears. Can coolant leakage get into the spark plug cavity and be causing the ceramic to crack or short out? Any suggestions/ideas?

Any help Appreciated
Citrusflight
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if you blow a head gasket, coolant can actually leak in between cilynders and foul plugs

 

Thanks. Right now I have a poor mans solution . Dielectric grease on the plug and it's running fine. I will pressure test the coolant to see if this is the culprit.

 

Is there any update? Have you found the solution yet? I am curious because my truck has been missing at around the same speeds as well..i have a 95 F150

 

This is a 2 year old thread.