When it is hot outside my f-150 king ranch missed////this is on the way to work when the sun is blaring down and it is 90'...when I go home at 11pm it is cooler maybe 75 and it runs like a million dollars anyone have any ideas

 

90 degrees of dry heat or is the weather very humid? Is the truck stalling on you or just chugging?

 

chugging jerks like its out of gas fuel filter changed 4 months ago

 

also today it is 85' no problem....

 

Your ECU maybe thinking it is over heating and goes into overheat mode, reduce fuel, higher idle. Or fuel system trying to vapor lock? Keeping the tank full keeps the fuel cooler.

 

What throttle positions does it do it in? Also, all gears? Misfire problems associated with bad COPs or fouled plugs usually show up around medium load on the engine and are more likely when its warmer. If you have a tuner keep it connected and datalog any misfires to determine if its coming from one cylinder or all, that will help narrow it down to a bad COP/plug, or something else.

 

could also be you throttle body, except I think you would notice this problem more than just on 90+ degree days if it was, however it might be worth a shot to try to clean the throttle body either way. this should also more air to get into the engine, allowing more combustion, and less chugging.

question; Does it chug on you only at when you are idling and going at slow speeds, or is it while you are at cruising speeds too?

AR