I have a 04 5.4 f150. when i get up to about 40mph or above and coast. RPM's drop down to about 1200 then when i ease back into the gas the truck shakes and makes a low pitch from the exhaust. also when WOT i get misfires and hesitations. help??

 

You might want to take it to say Auto Zone and have them scan it for codes even if you CEL is not on. I have the same engine and my truck does the shaking easing back on the accelerator. I had a code for my TPS and my CEL was not on either. I would start there and that should point you in the right direction.

 

I agree on getting the codes read. How many miles are on the truck?

 

Thanks suttonjr7! I'll do it soon. I have 65000 miles on it. Ive been told it was the coils and also the spark plugs. But ill have to get codes. I feel like i have lost power too.

 

No problem man. From what I understand the PCM should record misfires and it should say which plug or cop it came from. According to a mechanic at one of the Ford dealers in my area.

With all the electrical stuff and sensors that are on vehicles now a days I think getting codes read is where to start. I have so many times tried to fix something hoping it would help and wound up making it worse.

I am in the middle of trying to get my PCM flashed to see if that helps my vibration problem. Can't seem to get the tech to call me back with how out of date my PCM is. I wound up having to replace my throttle body.

Good luck to you.

 

did you get your 50k tune up?

 

Becareful if you try to change the plugs because they break sometimes. But at 6500 miles they should be good. And sometimes it takes a pretty bad miss to throw a code. My dads 4.6 had a bad miss for a week before it threw a code. And I had to put it the floor goin up hill to get it run the code.

 

have 85,000 miles on my truck and had the same problem until yesterday. finally got around to changing my plugs with new motorcraft ones and problem went away. truck feels brand new again and has all the power back. didnt break any plugs either just made just i soaked the holes with PB before hand and all came out nicely.