Throttle Position Sensor - Voltage Range

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I need somebody who knows a bit about 87 LM coding to answer a question for me (I'm lookin at you ShelGame)...

Over what voltage range does the logic module read the TPS sensor? I know it's a 5v sensor but it after reading data on my OTC scanner it appears the operating range is much narrower than 0-5 volts.

The reason I ask is a bit strange: When I bought my 85 Omni it had been converted to TII using an 87 CSX throttle body. The throttle cable actually had spacers installed on the cable at the accelerator pedal to ensure the throttle blade opened fully (Cable stretched? Too long? Don't know). BUT when the pedal was on the floor and the TPS voltage dropped below something like 2volts, the car would shut completely down until you backed off the pedal. It SEEMED as if the TPS voltage was exceeding the logic module's range and the LM was just shutting down.

I pulled the spacers off the cable. As a result the throttle blade does not open to full stop and the TPS voltage @ WOT never drops below 2.4v... AND the car no longer shuts down. Did I fix a real problem or did I simply bandaid a problem by keeping the logic module out of WOT?

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Wait a second... every thread I search seems to have the TPS voltage acting opposite of what my OTC scanner is telling me. My scanner says TPS sits at 4 volts closed and lowers to around 1.3 when the blade is fully open. Is the OTC scanner translating something or is my ---- wired backwards?

[86Shelby]

Sounds like it might be wired incorrectly. It should read ~1V at idle and 4.5V+ at WOT.

As for the pedal and cable... I found that it really helps to use the cable and throttle body bracket from the same car, preferably a P-body when doing a TII swap on an L-body. I had a similar issue not being able to get WOT using some random cable and throttlebody bracket(even tried using washers like your car haha); once I grabbed the bracket & cable from the same car I had no issues.

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Well after looking up the TPS operation it DOES look like my car is sweeping in reverse (unless the OTC scanner is inverting the voltage or something strange).

So I guess my question has evolved into: If the TPS was showing 4 volts at idle would the rpm tend to race? And if the WOT dropped to 1.3v with the throttle blade wide open would the car cut completely out?

[Turbo3Iroc]

Does your O2 voltage fluctuate at idle?

[86Shelby]

Oh yeah, that will cause all sorts of issues.

The comnputer is seeing low throttle opening voltage when in reality the throttle blade is wide open. Spark and fuel will be all out of whack.

[Opticon]

Judging by the scanner the o2 voltage tends to stick to one side at idle... the old sensor stuck lean, the new sensor sticks rich. I guess that's because the ECU thinks the car is in WOT.

[Turbo3Iroc]

Yeah, I'd rule out an issue with your OTC then.

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Inverted TPS voltage was the problem. Idle, cutout at WOT, and all sorts of fuel issues were fixed after switching two little wires. Wish I had noticed that sooner. The car was so rich the 1 week old oil was black and full of gas.