Hoping someone can give me some guidance. I have a 2006 f150, 5.4 4x4 with 130k miles. It has started to stutter/misfire while on the highway, usually as it gears up to pass. The check engine light NEVER comes on. Last summer I had all plugs replaced.

I took it to Ford and after two days there, they were unsure but said ALL 8 cylinders are misfiring. They guessed it might be the cat, but not certain. Took it to another mechanic and he thinks its not the cat, but is not certain on the cause either.

The hesitation always occurs around 30-55 mph, when I excelerate, like Im passing another car. As I give it more gas, it will go away, until I drop speed again and encounter another excelerating situation again.

Any advice or suggestions on what could be the cause?

 

Is there a certain RPM range which this happens at? sounds like it could be a timing issue.

 

it usually occurs between 3-4k RPMs, but as long as slowly accelerate, it never occurs.

Still puzzles me how all 8 cylinders could be misfiring, but the truck runs great while idling and at steady speeds. At this point, Im thinking the dealership must have been mistaken. I would think of the problem was with the cat, the stutter would occur more randomly as well, not just in hard accelerating situations.

Had a second mechanic look at it yesterday, he thinks it might be the headers.

I plan on taking it to another local Ford Dealership next week for a third opinion. At this point Ive become a little irritated, Ive received recommendations from mechanics to replace the engine to replacing the cats, all without a check engine light ever coming on. I did notice this week Im using alot of oil. In a 6 month time, I was 4Q low, with no noticeable oil leak.

 

Scott,

I have an 2006 with 5.4 and had the same issue. What solved mine was replacing the plugs going from ht1 to ht15. this helped then it was determined that the cam follower was bad on 4 replaced that now they are saying oil pump is bad and need to replace the engine.