jj_boulianne

So here it goes hopefully this will help solve the problem.
I have a 2004 fx4 5.4 with 146000. I have a roughy idle problem and a misfire problem as well. The rough idle seems a little worse when the engine is warm. As for the miss, it is very particular. When I'm driving down the hiway at about 80 km/h and slowly accelerate I get a sudden jar and the it's fine and then it happens again, until I press harder on the pedal and the RPM's go up and it shifts Into the passing gear. On occasion, while going up a hill it will act up. If I press on the pedal hard enough it will shift right away and no problems, but if I let the speed drop and slowly accelerate it will do the sputter / jarring issue. Once it starts it will usuall continue until I let off the gas. The CEL sometimes flashes and then goes out. So the last time this happened I kept my foot on the gas to see if I could get the light to stay on. It did I was going about 130 by this time. Turns out it was a missfire on Cylinder 4. About two months prior to this while pulling my 21' trailer I got the sudden jarring / sputtering CEL started flashing I let off the gas and pulled over. Looked and smelled everything seemed ok. Then going up a hil same thing only this time light stayed on so I took it to the dealer and found out it was a miss fire on cylinder 4. Tech said it was probably the coil so I went to the parts store and bought one and changed it. But now here I am again I get a sputter when simply accelerating slowly or on a hill?? I'm trying to rule out things as I don't have money to pour into it.

05 4x4 Triton

Have you changed the plugs because if not I would recommend that asap

A&M F150

I would definitely say plugs, possibly a bad injector, and a real stretch, you got a bad coil. It's rare for new, but it does happen.

bleufox99

i would check to make sure all the coils were completely plugged in before anything sometimes the silicone gasket in the connector comes off a little and when you plug it back in it doesn't seat properly, also the locking tabs can break and the connector will come loose causing a rough idle and misfire.

bleufox99

or ask the dealer if they can run a "power balance" on your truck and that will narrow down the cylinder with the misfire

Bennyv83

Guaranteed its the spark plugs. Mine did the exact same thing.

jnjh64

What is the correct plug gap for a 2003 F-150 5.4 engine? The auto part store said it was .059 and my Haynes book says, .054
What should I use, the auto part store setting or the Haynes manual?

Bennyv83

There's almost no difference... Split the difference!