Stang Runner, the TPS for the 5.0 is technically not adjustable, but because of some loose tolerances, it is somewhat adjustable.
You need a digital voltmeter. Using something like two safety pins, pierce the insulation of the green(+) and black(-) wires going to the TPS. With the ignition in the on position, make sure that the voltage is .97-.99 volts. Move the throttle level forward slowly and make sure there are no odd jumps or flats spots (Not likely with new TPS). It should go up to 4.6volts. Then, release it back slowly and make sure it drops to .97-.99 volts.
If the initial voltage is too high or too low, loosen the mounting screws and rotate the TPS until you get the correct voltage. Tighten the screws down and repeat the above verification process.
Then, reset your computer by disconnecting the neg battery cable for 15 minutes. Reconnect the battery and start the car with all accessories off. Let the car idle until its idle is stable at a specific RPM. Let it idle for an additional two minutes. Shut down for a couple minutes, restart and then repeat the same process with all accessories on. Go for a drive and see how it runs.
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351W 89 Mustang GT Convertible