I have a 1999 ford f150 with the 4.6. It is missing, during accelerationafter it warms up. It has 157k miles. Could this be a COP problem, or an O2 sensor?

 

could be the COP or u got water down past the boot like is also common. just pull the coil pack off see if the boot is wet

 

Does the boot you are refering to part of the COP? and if so, does this have to do with the routing of the air conditioner lines, and condensation leaking down onto it. I tried to look up the TSB dealing with this issue and could not get a complete copy of it. Thanks for the help.

 

yeh that sounds like ur problem i have a problem with the fresh air inlet at the top of the hood. it leaks down right onto number 3 plug when it rains. imma make a splash sheild for it this weekend

 

My particular engine does not have COP's. Today I am able to give a better description of the problem. After driving for about 20 mins., if I decelerate and attempt to re-accelerate my engine stumbles, a lot. It will continue to do this until the engine has cooled down and restarted. If I keep the rpms over 2k it is alright, but if I try to accelerate at about 1.3k rpm it stumbles really bad. When I give it more gas, and force it to downshift the stumbling stops.
Thanks for the help guys, this thing is driving me nuts.

 

id say a bad coil pack. if it was that it would probablt be acting weird and missing all the time not just when warm. have they ever been changed???

 

yeh coil pack or wire than. atleast the wires are easier to remove!

 

If you have a check engine light buy a tube of dielectric grease and fill the plug boot with it and reinstall to see if the fixes the problem. That should be the first step and cheapest. If no cel pull plug boots on all wires and add dielectric grease to all of them. From there if tha does not fix it I would buy plugs,then wires then coil packs. I hyad the smae problem only i was too stupid at the time too try the grease first. Anyway the dielectric grease stopped min from missing.
Mine is a 97 4.6 with 177k and know running fine.

Hope this helps.

 

It seems to only be happening in overdrive. Today I replaced the fuel filter(per Chilton), seeming to be the cheapest route. If I force it to kick down it stops stuttering. Only when it doesn't shift out does it stutter. Could this possibly be a sensor not communicating the the transmission telling it the downshift? Thanks for all the help guys.