Ok well I recently bought a 1998 f150 2wd with the 4.6. With 165k miles.

When I first got it I noticed it had a miss, put my meter on it and came back with cylinder 8 misfire. It is not a constant miss and much worse once it has been running for a bit. Engine makes no odd noises to indicate timing chain issues.

Has a new coil pack, pulled the plug it is an autolite double platinum that looked almost brand new, wires look new. Swapped with another wire from a different plug and still number 8 misfire.

Plug hole appeared dry with no oil or moisture.

Kind of at a loss for this one. No other codes or pending codes.

 

Looks like someone has already tried to solve the misfire, eh?
I'd keep swapping. Swap that plug with another hole.
And swap the coil packs side to side.
And swap the #8 injector with another hole.
If it STILL comes up with a #8 misfire, might have to do a relative compression check to make sure there is no mechanical issues.

 

Think I may have this issue worked out. After some swapping and pulling and reconnecting of different plugs and harness connections... drove it about 50 miles without the miss...

If this holds out its time to start thinking about putting all new timing components and new oil pump since the engine does have some age/mileage.

 

Id check the compression in that cylinder first. why put an oil pump in it? if the oil pressure is low, its 99% of the time excessive clearances----the oil pump wont solve that.

 

If I am going to be in there putting new timing components I figure I might as well put in a new oil pump while I am in it. It would be more of a piece of mind thing knowing it's new since I have known a couple of people who had their stock pump go bad close to the 200k mark.

Also when I tore down the 5.4 in my Expy the timing chains were not making racket but had enough slack that they had actually damaged the housing of the pump.

I have gotten the miss worked out and fixed.