Well I have researched every misfire thread in this forum I believe and cannot find a match to the problem I am encountering.....

2001 5.4 super crew 4x4....150,xxx on the clock....I noticed a slight miss under load in overdrive and nothing else...well after a month the CEL came on misfire on #1...no big deal right easy fix still has all the factory plugs & coils on it. Well after changing the coil, plug, & injector. Every time after resetting the ECM after about 30 miles the CLE comes back on misfire on #1 every time. There was a spat of about 4 days where the light never came back on (200 miles) then boom there it is...I checked the resistance on the injector socket & coil socket and every cylinder is good so there's not a short in either harness. I even warrantied the coil for another new one same thing...checked the plug it looked good (motor craft premium).

The truck runs great the only time you can feel a miss is when the truck is sitting idle in park or in gear...just a o so slight shake you can fee. nothing that affects the drive-ability at all.

I checked for moisture and its all dry....put die-electric grease on every electrical connector on the coil & fuel injector harness, cleaned the throttle, MAF and IAC......but the ECM always only has 1 error code....misfire #1.

The only odd thing the MAYBE could have contributed to this I think would be that the truck was about a Gallon low on coolant and read a little above half on the gauge for about half a day so I topped it off & haven't lost any for almost a month......thinking maybe she was eating coolant but that's not the case.

Any help or experience with this little headache would be appreciated!

 

Check your pcv tube that goes into the rear of the intake check that elbow and see if there is a crack or a hole might explain the misfire codes

 

It's been a month since you replaced the plug and topped off the coolant and there's no sign of coolant on the plug on in the plug well, correct?

That kind of misfire is almost always a leaking intake gasket on these.. if there's any sign of rusting or liquid on either side of the plug that's most likely what it is.

 

I think I found my needle in the haystack, the junky duralast coils I have been getting do not have a snug fit with the coil harness connector or at least on #1. I noticed it doesnt "snap" when I put it on...so I swapped #1 & #2 and the #2 connector was really a better fit for the duralast coil and its running stellar so far...I guess the #1 connector had been pulled off & on so many times it didn't like the aftermarket coil connection.

 

The connectors break pretty often, I didn't think about that. You can get those coil connectors from the dealer, or what I do is wire tie those suckers tight.