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Problem with TPS voltage

Old 01-07-2019, 04:56 PM
Thread Starter
Join Date: May 2005
Location: California
Posts: 221
Car: 1991 Z28 Camaro
Engine: 5.7L V8
Transmission: auto
Problem with TPS voltage

These electronic/computer/fuel injector cars can be a bit of a mystery. It's like a series of dominos, or a game of janga- everything trips into another thing... ANYWAY, my car failed smog because of high idle and timing at 16 degrees BTDS instead of 6(!). I set the timing correctly, but when I checked the TPS I found an issue.

There is only one machine screw holding the TPS in place- the bottom one has been sheared off. Now I know the voltage should be 0.54v, +/- 0.07 something. Even when loosening the one screw and moving the TPS as far as it will go, I can not get the voltage below 0.66v. If the outer limit of the tollerance is 0.61 or so, is my voltage worth sweating about- and will it cause any other issues?
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Old 01-07-2019, 06:03 PM
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Join Date: Dec 2004
Location: Mile High Country !!!
Posts: 11,634
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Problem with TPS voltage

If this is on your 91 .67-76 is the spec.
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Old 01-15-2019, 03:27 PM
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Join Date: Nov 2004
Location: Lansing, MI
Posts: 328
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Problem with TPS voltage

Originally Posted by Tuned Performance View Post
If this is on your 91 .67-76 is the spec.
Yup, learned this recently that the SD cars had a higher base voltage. Timing advanced that far will cause a high idle. You should replace the screws, get it set in properly then do an IAC reset procedure.

First thing to check would be to unplug the IAC when warm and see what your throttle set screw will allow it to come down to. Without the IAC and warm... it should be a low RPM. Neighborhood of 500-600RPM. If it's not, the IAC wouldn't be able to bring the RPM down.

Do you have any kind of scan tool that you can see what the IAC counts are?

You want to IAC to control the idle...

While talking about the IAC, a good cleaning of it and the passage way could be in order as well.
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