I have a 2005 with the 5.4 and it feels like a miss fire but only under load. I have new plugs in it and new fuel filter. I was going to change coils but someone had said something about a vaccum leak. Any ideas?

 

Plugs and COPs should usually be replaced at the same time. COPs get weak over time and can cause a low mis fire without a code popping up. Change the COPs (look at Global on ebay for reliable, low cost COPs. DG511 is the number you'll need) and check for vacuum leaks while you're in there.

 

What do you mean COPs

 

The things on top of the plugs are COPs (coil on plugs). Coils and coil packs are old types of ignition components.

 

Oh ok thats what I"m changing now. I"ve got 219000 km on it so I guess its time. Thanks

 

hey there, i'm kinda new on here, but i'm having the same problem, but
i replaced the cop's as well. revving the engine in nuetral no problem but
driving or doing a brake test it starts missing at about 1300 to 1800 rpms.
wasn't doing anything until after the tune up. have an 03 scab with 5.4l, 4x4. any ideas. driving me and my brother bonkers. any help would be appreciated. thanx

 

What plugs were used for the change and was di electric grease used in the coil boots? Trition motors are picky on what plugs they like.

 

Youve got a coil going out, it just isnt bad enough to set the light yet.

 

I used motorcraft plugs. And after market coil packs. And didn't put any grease on them. Suzukirider was right on that. My brother put the old coils back in and is running perfect now. Turns out that the after market coils were bad. Thanx for the advice guys.

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