ok please bear with me I have a 2000 f350 5.4 liter I recently fixed a misfire in cylinder 1 since then every morning the truck runs perfectly fine however at night when I leave work around 6 o'clock the truck has a misfire again I stopped pullover pull the spark plug out put the spark plug back in and it runs perfectly fine all over again please help me I don't know if this matters but when I replace the spark plug I only replaced one and not all 8 same thing with the new coil pack I don't see how that could cause this but if anyone knows better please tell me

 

To clarify, you're getting this same issue when a new plug and/or a new COP is used?

Are you reusing the same rubber boot on the end of the COP? If so, the boot may be defective.

Also, you could have an intermittent connection going on with the COP connector.

 

I would replace every plug boot. Every time I had a misfire on my old '99 V10 F350 it was always attributed to a plug boot deteriorating.

 

no I replace the coil and the spark plug this past weekend and I just pulled the same one up and put it back together and then around 6 o'clock when I leave work the issue continues but again I just pull it out and put it back in and it goes away

 

the plug boot is brand new though on this one coil

 

 

How many miles are on your engine? What brand plug and COP are being used? Are you applying die-electric grease to the boot? Anti-Sieze to the plug threads? Torquing the plugs properly? Is it the cylinder under the wiper cowl?

Below is a link for a possible solution if you are getting water or moisture between the plug and COP. I willd be applying the o-ring method next time around for my plug swap.

https://www.ford-trucks.com/forums/1...s-the-fix.html

 

Well I dont know if this is even the stock motor. The truck used to belong to BNSF, then my father in law bought it. I am the 3rd owner. The tach says 340,000 miles.
The brand of coil is Master something, not MasterCraft though, i was looking at the box this morning, I check on break in about 2 hours. As for plug itself, I'll have to get back with that one too. I am applying the anti seize and die-electric grease. Is there an amount i should use vs not use? Also, no the cylinder is #1 and its the front left one.

 

I'd go back to the COP and make sure it "snaps" or locks properly on the wire harness. Others have seen the same thing when not fully locked on.
And to Bently's point, check for moisture in the plug cylinder hole. A leaky intake manifold will allow enough coolant into the plug hole to help ground out the COP.

 

Exactly where on the spark plug did you apply anti-seize compound? How much?

 

Master Pro? O'Reillys house brand. I would recommend motorcraft for these parts. Time and again people use inferior/cheaper parts and end up regretting it.

 

r2millers: Yes sir the plug is dry when i pull it from the motor so i dont THINK any moisure is affecting it but i may be wrong. How do i know for sure?
redford: I applied the compound to the threads on the plug, all the way around the threads.
Bently Coop: YES SIR it was a Master Pro, I just went with it, because it was right by my house.

 

Im going to O'rielly now to get the Borg Warner upgraded unit. Sorry i probably spelled that wrong

 

Sounds like you recently fixed a misfire in the #1 cylinder, is this new misfire setting the CEL and you are always reading cylinder #1? On my 4.6L I was getting random misfires under load the CEL would flash but not always set a code, I was able to use a OBD reader that would display "pending" codes and found out it was random. I finally changed the POS two piece spark plugs and everything has been good the past 25k miles.

 

What do you mean two piece spark plug?