I have a 93 f 150 that has a rough idle. It is misfiring. I replaced the plug wire, rotor and cap. When I replaced the plugs i noticed the driver side plugs were a white color and the passenger side were black. what would cause it to be lean on one side and rich on the other? could it be a coil? I cant tell if it is a ignition or fuel problem. Thanks

 

could be any number of things, check for vacuum leaks at intake and hose connections, when the plugs were changed were they gapped correctly? how did it run before it developed the rough idle?

 

it developed the problem when i was on my way back from ohio to NY so I changed the plugs, but didnt help at all.

 

oh yeah yes i did gap them

 

If it has separate HEGO sensors for the right and left bank then the one that is running rich is probably defective. You would need a scan tool to monitor the operation to tell for sure.

Ignition components cannot make an engine run rich or lean, but they can cause fouled plugs.