Hello all, hope someone can help. I have a 93 F150 XL work truck with the 4.9L engine and 5 speed manual transmission. The last year or so I have had an intermittent miss after the engine reaches operating temperature. It is worse in the rain so am suspecting an electrical problem. My truck has dual gas tanks and the problem exists on both. The truck only has 72,000 miles and I have replaced all the usual suspects, wires, plugs, etc... The one thing I haven't replaced is the O2 sensor. Could the O2 sensor cause a problem like this? Thanks for any help.

 

Does "etc." include the cap and rotor - and did you use a dab of dielectric grease in the plug and cap boots?

 

Yes the cap and rotor were replaced also. The plug wires had a little grease on them. Maybe not enough? Thanks

 

A high probability there could be a harness rub-thru between two leads or to ground.
Run motor and move harnesses around, move sensor connectors etc.