My 2001 F150 with 4.6L started missing only on exceleration. I changed the plugs and the boots still misses when I give it gas, if I am cruising on the freeway or in town it is smooth as silk press the gas down 2inches and it stumbles and bucks. Smooth idle as well. Any thoughts?

 

The only two things that cause a misfire on exceleration are ignition faults or fuel. This happens under the load of accelerating. Do you have any codes showing with a check engine light on? Try cleaning the throttle body and adding some fuel cleaner and see if it clears. You can also clean the MAF sensor. The other issue is the coil pack but you will usually get a CEL showing on the dash. Any parts store will scan the truck for you and see if there are codes stored in the computer.

 

Hi.

Original COPs? How many miles on the truck?

What brand plugs did you use? Dielectric in the boots?

Get codes read, and post them. If the parts stores can't pull any, you may have pending misfire codes stored that need a more advanced diag scanner to pull ( no CEL ).

Be prepared to swap out all the COPS as a preventative measure. Motorcraft or Visteon only. No crap fleabay junk, no Accel, etc

good luck

 

The truck has 190k used motorcraft plugs and no I did not use dielectric. Was CEL but went out yesterday. Will pull code if any and try cleaners. Let you know Thanks

 

Hi.

Not using dielectric will almost ensure you will experience multiple random misfires over time.

This is a crucial step that must not be overlooked. Recommend at some point soon that you apply and re-install the boots, apart from whatever else you do.

Here's the correct way to apply it:

https://www.f150forum.com/f38/recomm...2/#post3272459

Skip the fuel additives - it will not help in this case.

Good luck

MGD

 

thanks I will go back and apply the dielectric this weekend.

 

Went back and added dielectric to all boots and plugs just as the thred dicsribed. still missfires. Finally got code reader in mail and i plug it in and nothing on code on nothing like no power to OBD port ? Any help could it be fuse?

 

Found it . It's #3 replaced it and got 2 codes 1. 0306 missfire cyl 6 2. 0456 small leak evap sys. I will get to work

 

moved COP to cyl #1 waited for CEL reread code misfire cyl #1 replaced COP runs great thanks for the help.