Basshead89

I just dud the full tune up 2 months ago.

now I have a miss under load... mainly when in overdrive and the engine is lugging.

I did cap and rotor, egr valve... new plugs (motorcraft copper ones) and new plug wires.

And it only seems to do it when it gets warmed up. It Idles perfect and free-rev's perfect.

It didn't have the miss before the tuneup...


Edit.. I gapped the plugs to .052-056..

Searching further I am seeing .042-.046 (ugh!)

Should I change the gap or should I keep looking for the issue?

edit 2...

no crossed wires at the distributor, I know about that issue.

dirtcrew51m

Ford can run gaps to .060, spray some carb cleaner around to see if there is a vacuum leak, did you bang a plug when you put it in closing the gap? Check to see if all of the wires are on tight you can also look at the engine in the dark when it is running to see if there is a spark leak.

planehunter

I too would double check a plug wire connections and verify that the plug wire routing is as specified. Might be getting a cross fire under load.

Basshead89

No crossfire, and no vacuum leak. I had already checked for them.

The culprit in my case was a bad plug. The ceramic had hairline cracks in it.

That explains the misfire only under load and warm.

planehunter

Glad you solved your problem. Thanks for sharing your results.