bluekim7

Hi guys,
I am new to the forum.
My truck is a 2003 f150 with a 5.4 engine. It has a misfire on cylinder 4 and I cannot figure out the problem. It first started out this winter and would idle rough for abotu 30 seconds when started cold, after that it smoothed out and ran great. It eventually got worse this spring and started to do it everytime I started it. Now it has a misfire on cylinder 4 all the time and through the comlete RPM range.

I have done several things without an progress.

1. replaced coil and plug. Plug appears to be burning pretty good. Not wet at all. Could of had a slight whitish residue on part of the plug.
2. Swapped fuel injector from cylinder 1 and cylinder 4.
3. Checked compression and got 140 PSI.
4. Swapped coils around between 2 and 4.
5. Disconnected coil connector and truck ran much worse.
6. Disconnected fuel injector connector and truck ran much worse.
7. Pulled out PCV and truck did not idle any different or in the rpm range
8. checked hoses for vacuum leak and could not find any visually or by wiggling hoses around.


From here I am lost and don't know what else to do. If you guys have any ideas please let me know.

Thanks,
Kim

RahX

Hmm, stab in the dark...Are you using Bosch platinums? How is compression on your other cylinders? Rule of thumb is 10% deviation between all cylinders. It may pump out 140 but if the others are putting out 175+ something is wrong with that hole.

1996 Redneck F150

I had a issue like that with my truck. It was a faulty plug wire. That might be your problem, and it might not be.

bluekim7

got it fixed. Finally a misfire on a different cylinder showed up after a week of running bad. Replaced COP on cylinder 3 and now it runs good.

TAZMACK23

replace them all, the factory cop's suck. did one then two, finally replaced the all. runs great now. once one go's the rest are coming.

nemo

i have a 2001 so it is the one with the crappy coils. I just replaced a second coil....which means the other 6 will follow. It is about $400 a pop to replace one. Will the newer coils stay in better than the factory crap ones??? Is there anyway a person can check the coils on an annual basis to check to see whether or not they are going to fail soon?

I would have to take it into the dealer as i can't do mech work myself.

027700

i did the coils on my 02 and it was only 60 bucks a coil. you way over payed

027700

you dont have to worry about the missfire;. once it starts flashing the code just clear it a couple times and it might go away. i took my battery cables off the last time i got the code and after i put them back on i havent got the code again. and its been 3 months.

B.C.XLT

i replaced mine with a set of MSDs for about 300 bucks and it runs great