Ok ive exhausted all the threads and have been searching for a solution for damn near a year now. my ranger runs very rough at idle around 900 to 1200 rpm range in drive and 1500 in park. It dies at every stoplight and hesitates horribly when i step on the gas. Ive checked the codes on it and im getting a code 63 for low tps signal ive tried testing my tps to no avail and even replaced it twice. ive heard that the iac is a main culprit and gave it a good cleaning, it seems to operate fine when i checked the plunger. ive also repaired a vacuum leak on my pcv valve and replaced the hose. i recently dropped the tranny and repaired a lose bushing on my torque converter and replaced all seals filter and fluid. Im still pretty new to engine electronics so if you have any ideas keep it simple for me also i replaced all wires, and plugs.

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Stock 1988 2.9l Ranger XLT

what is your tps reference voltage, voltage to ecm at idle and at WOT? assuming that's a stored memory code(?) or was it KOEO or KOER? really recommend running a key on engine running test after checking your TPS voltages. it's possible that stop screw has been fiddled with, which should never be touched. check your engine vacuum w/ a gauge

well the reference voltage is around 5 volts but the tps is sending a steady 4.6-4.8 at idle and wot although i may be testing the wrong wires... and i do believe my buddy screwed with the stop screw while he was looking at it.

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Stock 1988 2.9l Ranger XLT

there's only 3 wires, ground, your 5 volt reference, and the signal after it's gone through the potentiometer. the more the TPS is twisted, the more of the reference voltage it passes back to the ecm to determine your location on the throttle. if the voltage doesn't change whether you're at idle or WOT, that's definitely a problem. it should be reading around ~.9v idle to ~4.5v at WOT.

I wonder if you did have a bad TPS, and maybe the new one was not installed correctly in regards to the throttle plate(?)

big no-no adjusting that stop screw, has nothing to do with setting base idle. the computer is 100% responsible for the idle speed. there's a procedure for re-setting that around, but I can't remember off hand.

Well you might be right about the tps. i think i might be getting faulty parts from auto zone as most seem to be broken out of the box... ill look into resetting the stop screw, and getting another tps from somewhere.

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Stock 1988 2.9l Ranger XLT

was your code key on engine off, stored memory, or key on engine running? stored memory, you might have had a bad tps. two new bad tps sensors in a row ?? double check your voltage back to the computer, if high no matter what, I would start questioning whether it was put back on right. not second guessing your work, but something doesn't add up here

It was key on engine off and I believe it was just faulty parts one was coming apart at the seams when I opened it and the other read 0 when I checked the resistance with a multimeter as the OEM had resistance which I can't quite remember. And it very well could be my work as I said I'm not good with sensors haha. Also today I thoroughly cleaned the throttle body and it seemed to run slightly better. I've also noticed a baffled sound from my exhaust possibly a clogged cat?

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Stock 1988 2.9l Ranger XLT

Have you checked your fuel pressure regulator? Pull the vacuum line to the manifold off at the manifold fitting and check for fuel in the vacuum line. I went through all the sensors on my '87 like you, turned out to be simpler.

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1987 Supercab XLT 4x4

Stone stock - bought new off the lot
2.9 V6, 5 speed Manual

Even though this is super late it did turn out to be a faulty fuel pressure regulator spitting fuel into the vacuum lines. really simple to check and made me face palm hard haha!

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Stock 1988 2.9l Ranger XLT