1993 TPS issue
 

Hi all,
I recently picked up a 93 in great condition with 154kmi.
It appears the car has been meticulously maintained.
When I test drove it for the first time I noticed the infamous TPS/IACV/Dirty/Throttle body idle issue, where it bogs down and dies when accelerating from a dead stop. I installed a new fuel filter, IACV and cleaned the TB.
The out-of-norm thing is, when I replaced the TPS, the CEL came on throwing a 21 and 41 code but the idle/accelerating issue subsided. HOWEVER, it was stuck in 3rd.
So, I swallowed my pride and tuck it to the dealer for a very expensive diagnosis. $200 later they tell me the signal wire is reading 4volts at closed. So, it's either a short in the wire somewhere or the PCM is shot.
For ****s and giggles I ordered another TPS from RockAuto just in case the one I bought from Oreilys was defective.
Should I believe the stealership and plan on chasing down a mysterious short or replacing the PCM?
I'll let y'all know if the NGK TPS from rockauto is the solution...
Any tips/feedbak greatly appreciated.

updates:
swapped TPS and she’s started running like she’s supposed to and cel went off immediately.
however, after driving it around all day yesterday the cel is coming on/off sporadically. I’m going to replace the IACV with a new one from rockauto and see what that does.

Measuring the signal wire unplugged from the TPS, you'll get around 4-volts. Try measuring the with the TPS plugged in. You can also set the meter to read ohms and measure the TPS sensor between the signal wire and either ground or the 5-volts to see if it's bad. Also verify that you have a good ground and +5volts to the sensor. The ground for it is with the other wires grounded to the engine block over by the dipstick (good idea to take that apart and clean it regardless). I wouldn't be surprised if the new one was bad.

thanks for the feedback. I’ll tear back into it when the new TPS arrives.

I agree on testing the tps plugged in with ignition on. Simply back probe signal wire and check the parameters again. The fsm specs are minimum 200mv closed maximum 4.8v wot. The voltage should smooth and steadily increase while opening throttle plate. Before that test the connector for 5v, ground strap from block to firewall, and proper resistance. 200$ for that test ouch..

New TPS from rock auto arrived today. I swapped it out quick and drove it up the road to the gas station. Issue subsided immediately and check engine light went off.
She’s running like a new car!
thanks for the help guys.
I’ll be posting pics and a build thread in the next few weeks.