Sometimes when I start the truck it misses real bad and spark knocks for several miles. This only happens about 4 driving days out of a week not all the time. I put on a new distibuter cap, rotor button, fuel filter and air filter right before this started. Since then I took it to a shop and it would not act up with them to diagnose. It runs great sometimes!!! I started backtracking the recent tune-up and put on new wires, another distributer cap and new plugs. What is going on here? It has always had a surge in the motor at idle but this is something new. If I shower down on it and get it through all the skipping it runs decent.

 

Check the fuel pressure at the rail and test the coil according to Haynes' procedure.

 

Hello,

I THINK I may have your answer. Check your spark plug wire
routing. These motors are prone to crossfiring. Reroute your wires so that none of them are parallel, or close together, and your problem should be solved. Cheap and easy.

Hope this helps.

Tim in Detroit
95 f-150 2wd s.c. 5.8, e40d

 

I've had that kind of trouble with them newfangled spiral core wires. They seem to be very sensitive to how they're routed.

 

If you have a 5.0 make sure wires 7 & 8 are not routed close together. You may want to verify timing is also set correctly. And run a can of BG 44K thru with your next fiill-up. Gets reid of carbons deposits on pistons and combustion chambers.

 

might want to check the timing. Also try running a can of fuel system cleaner or combustion chamber cleaner... it may be some deposits are causing it to preignite by staying heated up during the compression cycle and acting like a glow plug on a diesel.

fyi: I had the experience of pinging getting worse while the combustion chamber cleaner was in the gas, and then better on the next tank.