I have a 2000 F150, 4.2 V6 with 67k miles on it.. Here the problem im having.. :
Depending on how it 'feels' when it starts, acceleration may bring one of two results.. One- Normal... or two, cutting out, falling on its face on heavy accel. Light accel everything is hunky-dory. Even while driving, putting your foot into it will cause this stumble (miss, etc).
Sometimes.. every so often, the engine (when cold) will stand on its toes and be extremlely sensitive to the pedal.. you can hear the RPMS and feel it.. However, once the engine heats up, the power it gone.
It feels like it may not be getting enough fuel, BUT
it varies depending outside temp and engine temp (usually everything is fine when engine in cool and or its cool outside).
No Check Engine Lights... No codes.
Also, When it is really hot outside, even some 91 Oct fuel (always with less octane) i'll get a 'pinging' on light accel while driving. Once at driving speed if I lightly press on the pedal it 'rattles' and pings.
Some have suggested the TPS.. some the MSF sensor (cleaned it).
Any ideas... I am considering replacing the TPS just for spite.
Thanks in advance!