I have a 1987 ford f150 with a EFI throttle bodied 5.0L (302), and I have taken it to a mechanic multiple times because for one it has a dead spot in the throttle and it dies when you let off the gas at a stop light or sign. But the mechanic said he checked everything he knew to check and found nothing wrong with it. I also had my cousin read the computer previous to this and we couldn’t pull the codes from it. Any ideas?
fuel pressure regulators would often stick on those. Check the pressure. Make sure the EGR solenoid isn’t mounted upside down…they’d ( the sponge) get wet and cause full EGR at just off-throttle. Of course, TP sensors. Another icommon fault is the O2 senor gound not being put back or just broken…it should be an orange wiree and atteched to the intake manifold stud at the right and rear of the engine.
There’s always the possibility of there being more than one problem at work here.
The dead spot could be a TPS problem and the dying at stop signs could be a faulty Idle Air Valve problem.
A vacuum leak can also cause the above problems and the best way of checking that is by connecting a vacuum gauge to an intake manifold vacuum nipple.
Another possibility could be a faulty ignition module. This truck should be a TFI model (Thick Film Integrated) and if the timing is not advancing because of a faulty module a flat spot may be present along with a dying engine.
If the module has been replaced and the ignition timing set without disconnecting the SPOUT wire the timing will be way off. (retarded to boot)
I would add that the things I mentioned do not always leave a code in memory either.
Hope some of that helps anyway.
(Those modules are also very prone to heat related problems during the summertime.)