98ford5.4

I got a 98 5.4 and am haveing a shurging/vibrating/shaking problem when in od if im cruzing and give it any more thottle that what im cruzing at itl buck and surge all the way up to about 1/3 throttle then itl down shift and be smooth again it idles fine and accelerates fine just when gradually trying to speed up itl also vibrate at 80% throttle upon acceleration but if I let of a little bit itl stay at the same rpm but accelerate smoothly I am stumped
New motorcraft plugs no codes
I intalled a new motor and tranny about a month ago to the best of my ability (im only 17) but a local shop said it was all ok. Anyway its got a cai and longtube headers everuthing else is stock
I dont know if it air/fuel timeing or what?
Thanks for the help

98ford5.4

Bump

texasedition

Did it do it as soon as you put the motor in?

98ford5.4

Yea

98ford5.4

It also did it with my old motor just not as bad

deanofay

My truck did that at around 50mph when I would try to gradually accelerate. My coils were bad, I would check that

jferg92

Yep, i had it and this question gets asked daily. First suspect- coils

98ford5.4

If its the coils wouldnt it throw a code and the coils only have 60,000 on them

jferg92

Rarely does. Atleast take them apart and clean them with dielectric grease and see if that helps

khodgens

COP's don't always throw a code. Clean the tops of them. If any have a white thin line across the top it is bad, replace it. As previously stated clean real good and put a liberal amount of dielectric grease in the cap and reinstall.