brihunt

Help Please! got a 2000 with 5.4 that looses power and chugs down the road. Not noticeable at slow speeds when shes not working but once up to running speed it studders when on a hill or need to get into the gas even a little. New plugs. coil boots cleaned and greased. New fuel filter and cats were cut off today thinking they were plugged and causing to much back pressure. 148000 miles on her. Im stumped! It does seem to run better on the way home from work at 2 Am being 20-30 degrees cooler outside. Sprayed eathier around intake and no change so im thinking no intake leak

FSM

So under light load it runs fine under heavy load it falls on its face. Possibly have a bad coil or two or when the fuel pump gets warm your losing pressure and the colder temps could keep the pump running cool enough to run good.

brihunt

Exactly FSM! but isnt a coil just bad or good? would it only act up like that when theres a load on it? or wouldnt it pop a code for misfire? How to go about testing the fuel pressure if it only does it at crusing speeds??

FSM

A lot of ford coils only fail when they are under heavy load because they need to fire up to 60kv spark and multiple times to complete the burn. ford has a tool that can load test each coil or if you know someone who has a nice scan tool watch your cylinder misfires while driving duplicate the concern and you will find out which coil is bad.

FSM

A failing coil might not meet the threshold to turn on check engine light especially on a ford. I see it all the time. Fuel pressure you would need to hook a gauge up drive it duplicate the concern and see what your pressure is reading while it's acting up. Sorry for two posts

brihunt

thanks guys! my buddy works for a ford dealership and im sure can get it checked for me or he did just buy snapons new timing light that tests coils also. Ill see if that will work. Im about ready to rip my hair out! this is my baby and my only means of a ride. sucks driving it like this. scared im gonna hurt it more by doing so