68Datsun510

Hey all, so my 98/4.0/auto with 200K on it is driving me nuts, had the TCC diagnostic code when I got it, had the trans serviced by a reputable shop, the tech made the comment that "it looks like your converter is coming apart." because the fluid was in terrible shape, following PO740 diagnostic procedures, i checked the brake switch, and measured the tps, the tps had a smooth swing, but i discovered the wires were "heatrotted", the insulation cracks like crazy when you flex the wires, upon reconnecting, the tps is stuck at 19% and the idle is 1000rpm, finding a pigtail for this thing is a B&^$#, did the TPS go bad during the test, or can the cracking wires mess things up that bad??? Thanks!

letsgomuddin

Chances are, it is just the funky qiring causeing the tps problem. I know Chrysler has a pigtail for it, otherwise a boneyard is your best bet. Make sure you solder and heat shrink the connections, do not use crimp connectors.

SeriousOffroad

TPS does not control the idle speed. All it does is report the throttle position to the PCM.
Do thorough throttle body cleaning including removing the Idle Air Control (IAC) valve and cleaning the pintle and the corresponding seat inside the valve body.

Sounds like you might need to find a new mechanic. Any p0700 code should first be addressed by cleaning the contacts inside the neutral safety switch. There are many write ups on this forum and elsewhere on the Internet that explain exactly how to do it.

68Datsun510

I have had that on my to do list, no shop here will stand by a "clean the switch" approach, even the best just want to throw parts at it. Ill pull the NSS and get it done asap and report back.

68Datsun510

BTW tps unplugged, 700rpm idle, plugged in, 1000-1200 rpm idle, I know that it only reports, but its confusing the hell out of the ECU me thinks

SeriousOffroad

jpmarine6786

I would think because the TPS is screwed up the computer is thinking you're giving it gas and is injecting more fuel.

68Datsun510

Precisely, damn wires lol the Datsun's TPS is a cable and my right foot!

68Datsun510

Well I made a rather disappointing discovery, upon pulling back the wiring harness insulation revealed that all three throttle position sensor wires are in fact melted together from engine heat, I expect this to be a very common issue on these because they are same side intake exhaust engines?