Hello guys, I hope someone can shed some light into this. My procharged 2005 FX4 gets random misfires in first gear under full throttle at around 4300 RPM. During the misfires it gets a lean condition (13-13.5 A/F). I have changed fuel filters and cleaned all electrical connections of the COP´s. Could a COP have gone bad?? The misfires randomly change from cylinder 3 to cylinder 7. Will a misfire make the combustion go lean?? Could the belt be slipping??

Also, has anyone tried the granatelly high performance COP´s ??

Thanks for the info. This is a great forum ĦĦĦĦ

 

A Misfire will show lean AFR's. Did you run any Octane booster int eh truck? It seems to cause issues with boosted 5.4L 3V engines.

TG

 

Have you checked your plugs?

 

I had the same issue after a long drive back up to Alaska from Vegas. I had the Ford dealership scan and they showed a couple of bad injectors, but it was actually plugs that were causing the misfire. I had 5 of 8 plugs gummed up. I had some pinging while towing, and I had to use octane booster, so one or the other, or the combination of both, probably caused the plugs to go bad so soon.

 

Thanks for the replies... No octane booster was ever used on this truck, but the plugs are still the stock ones with the stock gap, could that be the problem??

Thanks again.

 

I'd definately look into getting a set of Ford Racing or Autolite HT0 plugs installed. Sounds like you have to change them out anyhow, so you might as well upgrade.

 

Where in Miami, Fl or close by can I get the Autolite HTO´s ?? Napa autoparts doesn´t carry them. Thanks again...

 

Definitely go with a smaller gap than stock.
Here's a good post for info on recommended plug gap:

https://www.f150online.com/forums/sh...spark+plug+gap

 

I think you can get them through lethal performance. They have a website, www.lethalperformance.com