I have an 05 f150 5.4 driving up Rd I lose power could only go about 20 in a 65 yippie. I limped it to O'Reilly the put it on computer and said cylinder 5-7-8 misfire so I change all 8 plugs and coils and now it will not start turns over but won't start any advise would be greatly appreciated thanks

 

You need to check for fuel pressure.

 

Check condition of the FPDM.

On driver's side frame rail above rear axle.

Easier to access and view with spare tire lowered.

 

X's 2. These corrode extremely badly and cause all kinds of issues.

 

I had this problem years ago while driving in Mexico. Turned out I was burning Mexican leaded gas and didn't know it. It clogged the catalytic convertors and was creating back pressure that caused misfires. A mechanic loaned me a hammer and cold chisel and I punched some holes in the convertors, all the beads fell out and the truck ran fine. This was the early 80's, pre-OBDII. I've since been told convertors can do this without leaded gas. They don't last forever although this was the only convertor problem I've had.

 

Done this and changed the fpdm and plugs and wires turns over but no start. Fuel pump is working

 

If you're familiar with the fuel pump reset button, check it. A little hard to access but not impossible.

Located in passenger side footwell fuse block - upper left area.

Use a cellphone camera to aid you.

Did the initial loss of power happen all of sudden?

 

Yes it was all at was when it done it I can here the fuel pump kick on and off it sounds to me like it's not getting gas and I just put 35 gallon in it really that before it happened
But I will definitely check that though thank u