Occasionally when i get out of my truck with it running i can hear the engine miss through my dual exhaust. It doesnt do it everytime around or constantly, but it is enough to worry me and my gas mileage has been down. It has fairly new wires and plugs. It is a 2000 F 150 4.2 xl. Would it possibly be my O2 sensors going bad ( they are on my list of replacements) or could it be something like my injectors or a valve. I have run a bottle of heet through and then a bottle of injector cleaner. It seems to do it most when it has been run and warmed then idling.

 

Also, it has no codes or check engine light on, and when it is missing, if i rev it to about 1500 rpm, it is rough but over 2000 it is not. When i put it in gear and go, there seems to be no problem.

 

What model year and what mileage?

My first guess: Spark plugs and wires.

What you describe is pretty a common indicator of the above mentioned items needing replacement.

 

I mentioned above that it is a 2000 F 150 4.2 xl. It has about 92000 miles but the plugs and wires were replaced about 15000 miles ago.

 

Sometimes there is no miss and sometimes it gets shakey but any ideas i could try would be appreciated.