ok so i have the 04 5.4 3v and it runs just fine until i go wide open throttle. then it starts spark knocking and skipping on number 5. (or so the code says) then it will keep skipping for a mile or so and start running fine again. im thinking cats maby? dirty fuel filter? idk just wanted to know if anyone else has seen this.

 

mileage? ever been tuned up? whats the build date of your truck? pull the front driver side coil(#5) and see if water is down in the spark plug bore. i'm thinking it'll need a tune up. how olds the fuel filter?

edit: the cats are fine but you cant drive too long with a misfire or it'll cause the cats to overheat and melt and get clogged up.

 

140000. 3/04 and i just replaced all plugs. its due for an oil change soon airfilter is clean. fuel filter was changed about 20000 ago. ill pull the coil tommorow and check that.

 

what brand plugs? and was dielectric grease used? while you have the coil out just swap it with number 6 and see if the misfire moves. and you may want to consider changing the fuel filter soon. hell it may be the whole problem, you never know.

 

So what's with the skipping ? Is that suppose to mean misfiring ? Or does that truck jump rope as well...?

 

misfiring. same difference. motorcraft plugs and yes dielectric was used.

 

I've never seen skipping in any service manual, but at-least I know what you mean.

 

oh its in there.. right beside the goodntight torque specs.

 

Hard to say with a 3 valve. Do the simple first = Fuel filter, Check pump pressure,Test the EGR valve (make sure it isn't hanging), Swap #5 injector w/#1 and see if the problem moves to #1. Do the same with the coil, if nothing changes.

If all that fails, I would take a look at the plug.

 

yeah i think thats the plan for tommorrow.

 

When you replaced the plugs, did you use the required nickel anti-seize on the barrel of the plug? If so, is it possible you used too much or got some on the ground or center electrode? I'd consider pulling #5 plug and looking at it carefully.

 

yeah i used the antiseize but i dont think it got anywhere it doesnt need to be. its been raining so i havnt done anything to it yet.