1978 ford f150 400m 3spd auto trans.
truck will idle fine for about five minuets then start to putter out like she ran
out of gas but will start again after a few cranks. when at idle, in park or
drive, when the throttle is applied lightly the engine will bog down and likely
die. i have to keep the RPM up for it to stay alive. there is also a noticeable
whistle that responds to engine speed; whistling at a higher pitch at higher
RPM and lower at lower RPM, what does this sound like to you?
Check vacuum line