Jonestown9

I have a 1998 F-150 with a 5.4 Tritan engine.
At the speed range of 35-45mph, the engine starts to lose power and hesitate. I have had new plugs, wires and spark plug boots replaced.

To my chagrine, this did not eliminate the problem.

I am going to have the fuel injection system get a thorough cleaning.

Anyone else have this problem and what did you do to fix it?

whitecrystal1

Maybe a coil breaking down under load?
Is it only speed related or could it be rpm or engine load related? What brand plugs did you use.

Jonestown9

The issue is strictly speed-related.

I do not know what kind of plugs were used, they were installed by my mechanic.

whitecrystal1

I ask because I have read a few threads where our trucks have had issues with Bosch plugs in them.

Are you getting any SES light when this happens?

Ty

I think the 3 valve 5.4's have the problem with those plugs, not the 2 valve.

whitecrystal1

Nope, the are a problem in the 2v's too. Randam misfires, fouling, causing the engine to knock.......

Jonestown9

I can check to see what type of plugs were used.
I do not get any SES warning lights when this hesitation occurs.

The truck was put on a diagnostic computer and nothing showed.