2001 f150 supercrew lariat 4.6 171k miles.

Had a serious misfire when i bought the truck, a friend came with me at time of purchase, he saw the pcv hose was damaged and told me to low ball a price of $3400, i got it.

Anyways it didnt end up solving the problem after hrs of looking around i finally dropped it off to a mechanic

He found 3 spark plugs were loose, he put all new plugs in, 2 injector o rings were leaking and one cop wire was needing repair plus he changed out sway bar bushings, bypassed my heater core (as i requested) and greased up a wheel bearing.

Charged me $250 for all above ... Good price??

On the way home i noticed it ran 90% better but had another misfire on cylinder 7, i pulled the plug on the coil pack and the injector (one at a time) and noticed immediatly change in idle.

The misfire i felt while driving was only when increasing rpm and speed not constant.

Could the coil pack be weak were its not firing correctly under load but seem fine at idle or steady speed??

He did use motocraft platinum plugs.

 

I would agree to Weak COP...they can really be boogers to find.

on another fourm they been having pretty good luck with... Search Ebay for "Visteon DG508" - a full set is about $180. Visteons are the same as OEM, it's European Motorcraft....but alot cheeper

 

After i posted the thread i went for a drive in a rain storm and when i started the truck immediatly it was misfiring as before it was only under load.... Then after i went through a few puddles #6 started misfiring... So after thr storm i hope no#6 will dry out but I will replace #7 for sure... We have tornado watch where im at.

 

sometimes #7 or #8 can be related to leaks from the heater hose connection at the firewall... just a thought. I also agree 75% of "misfire" on the 5.4 motor are related to bad COP.. i assume the 4.6 is the same.

 

Changed both 6&7 out and runs great now... Thank u all for your replies im assuming cop #7 was just done and #6 got soaked in todays flood storm....