1997 base longbed
138,000 miles

So, this has been going on for a LONG time. Between 38-42 mph the engine (ignition, whatever) "misses". There is a perceptible "skip". Under 38mph, no problem. Over 42, no problem. On the freeway and getting up speed (meaning I accelerate through 38-42), it doesn't happen. Only seems to happen if I "hover" between those speeds.

Spark plugs replaced about 10,000 miles ago. New sparkplug wires about 500 miles ago.

Any ideas on what might cause this?

 

Well it has spark plug wires . It must be a 4six or 4two. Am I close?

 

Sorry, I don't know what that means.

 

It's called a motor. Do you know which one you have there ? Only two of them have plug wires, which is it ? They are different.

 

Ah! I believe I have broken the code.

4.6L motor.

 

Did it do that BEFORE you replaced the wires/plugs or AFTER?

 

well...hard to say for the plugs.

As you might imagine with only 138,000 original miles, this truck is (was) used very infrequently. I don't recall the issue before the spark plugs were replaced. The plugs were replaced in...well, at least 5 years ago.

However, it was definitely "missing" before I replaced the wires. That was one reason for replacing them. They old wres were OE.

 

Well I just had some missing issues on my 99 4.6L and eventually I found the new plug wires I installed were tight to push on the spark plugs. It would misfire randomly when warm. Now my misfire was noticeable enough to send a code to the code reader which was able to point me to the cylinders in question. Hopefully you can get access to a OBD code reader. My fix was to remove the plug wires and reseat all the way down.

 

I considered that as well. Replacing the wires was such a pain in the *** that I am traumatized by the thought of going back in. Will address after a good nights sleep tonight (and a couple beers).

 

My guess is you DID NOT push the wires down far enough. I will use the handle end of my dead hammer to push the boot down so they will click. Also, use dielectric grease on the outside of the boot ridges to help slide the boot. Use a vacuum cleaner with a small diameter tube attached to vac out ALL of the GUNK from the years of neglect. You may have a DEAD killer bee down there.....really.
I've vac out some pretty big pieces of dirt before.