Hello everyone, I'm looking for some help diagnosing a misfire in my 02 Ford F-150 5.4L. The misfire only seems to occur when the vehicle is warming up, no codes or check engine light at this time. It seems to happen right before the engine reaches normal operating temp and only last for a minute or two. The vehicle losses power and shakes alot, While it it missing I smell gas in the cab and there seems to be an unusual amount of white smoke but no coolant loss at all. During normal driving I sometimes notice a slight misfire and loss of power but it seems to be alot worse in the morning. I have replaced all caps,plugs, fuel injectors, and fuel filter about 25,000 miles ago. Also I recently had the transmission repaired and the vehicle ran great all most to good, like the computer was re set after not having power for a week while it was repaired? After running it for a week it gave me a P0240 so I replaced the b1 s2 sensor. So now it has had this problem for over a week with no codes. She has 176,000 miles on it but ran strong before this. Anyone have a similar problem that may be able to offer me advice?

 

Did you clean your MAF? Also a gummed throttle plate could be the culprit. Also, try an extended program of sea foam to the fuel over a few tanks. That may help. Are you sure no plugs were damaged during installation? Like a cracked pocelain? Also a very light application of dielectric grease inside the boots couldn't hurt. Or you could have a bad "new" plug or coil

 

I'm gonna take a guess on this one. (Being sarcastic) seen many cat converters clogged. Un bolt the two header studs on each side and lower the xhaust so it's not connected. Take it for a road test. You will be surprised. Had one that drove me nuts. LMK how you make out.
Jeff.

 

ooh! Yes. I totally agree with the possibility of the cat being plugged. Didn't think of that. Good luck, hope that solves your problem.

 

If you can , consider this,
See if there are any codes stored in the computer. If so, the code(s) may identify the cyl(s) that are misfiring. If it is a particular cyl, swap the coil and see if the misfire moves to the new location. Before going any further it is necessary to know if you obtained any direction to pursue from the code(s). Need to know the code number(s).

 

Agreed with you !!