Erratic TPS Reading And Running Like Crap

[Scoobum]

Got a call from Dan today and his car is running like crap...and the TPS via SM is erratic. Bad TPS?

[earlbrown]

or wiring between the TPS and ECM.  Odds are it's the TPS.

[Scoobum]

Thanks Earl. Doing a Caspers order. Gonna get John to toss one in with the rest of the stuff.

[earlbrown]

It's always good to have a spare, but I'd back probe the one installed just to see.

[Scoobum]

Question. Dan picked up a modded ECM to run his old skool 83's. Is it possible that ECM is causing the issue? I have a known good ECM here I can try.

[Steve Wood]

It can be......I have seen it do it once....you can also put a meter on the tps and see if it is giving you the same numbers as the scan tool

[Scoobum]

It can be......I have seen it do it once....you can also put a meter on the tps and see if it is giving you the same numbers as the scan tool

We both know I'm useless at electrical.   I'm assuming you want me to probe the ends of each of the three wires...and the value should stay steady.

[TexasT]

I believe the value should move as you open the throttle plate(the tps moves)
I think at rest it might be like .42v and at wot 4.5 or so and should move steadily as you open and close the throttle. If it jumps there might be a dead spot on the tps. I think you can read it on a scan tool also.

[Scoobum]

I believe the value should move as you open the throttle plate(the tps moves)
I think at rest it might be like .42v and at wot 4.5 or so and should move steadily as you open and close the throttle. If it jumps there might be a dead spot on the tps. I think you can read it on a scan tool also.

Dan said with key on...the TPS value on the SM is jumping all over the place. It won't stay still. If you watch the TPS on PL you SHOULD see it move smoothly as you move the throttle. I'm gonna take my PL to Dans tomorrow and hook it up to this ECM I have. Figures the one spare part I don't have is a known good TPS.

[daveismissing]

Take a voltmeter and look at the wire that carries the 5v supply to the TPS -is that steady?

[Scoobum]

Take a voltmeter and look at the wire that carries the 5v supply to the TPS -is that steady?

Will check tomorrow. Which is the 5 volt wire?

[daveismissing]

When  you do what Steve asked you will have figured out the TPS and GND wires
So its the one left over...

[Steve Wood]

The dark blue wire is the signal wire

5.0v wire is the gray one

[Scoobum]

Thanks Steve. I'll get at it in the morning. Gonna freeze my ass off in the 32F temps tomorrow.

[Scoobum]

Swapping in a known good ECM cured the issue. Thanks for the help guys.