99SSragtop

I guess if your in your desired idle range your OK.

GM thinks otherwise.

The Throttle Position (TP) sensor is connected to
the throttle shaft on the throttle body unit. It is a
potentiometer with one end connected to 5 volts
from the PCM and the other end to PCM earth. A
third wire connects from a sliding contact in the TP
sensor to the PCM allowing the PCM to measure
the voltage from the TP sensor. As the throttle is
moved (accelerator pedal moved), the output of the
TP sensor changes. At a closed throttle position,
the output of the TP sensor is below 1.25V. As the
throttle valve opens, the output increases so that,
at wide-open throttle (WOT), the output voltage
should be about 4 volts.
By monitoring the output voltage from the TP
sensor, the PCM can determine fuel delivery based
on throttle valve angle (driver demand). A broken
or loose TP sensor can cause intermittent bursts of
fuel from the injectors, and an unstable idle,
because the PCM interprets the throttle is moving.
The TP sensor is not adjustable and there is no set
value for voltage at closed throttle because the
actual voltage at closed throttle can vary from
vehicle to vehicle due to tolerances. The PCM has
a special program built into it that can adjust for the
tolerances in the TP sensor voltage reading at idle.
The PCM uses the reading at closed throttle idle
for the zero reading (0% throttle) so no adjustment
is necessary. Even if the TP sensor voltage
reading was to be changed by: tampering, throttle
body coking, sticking cable or any other reason,
the TP sensor will still be 0%. The PCM will learn
what the closed throttle value is every time the
throttle comes back to closed throttle.

FiredUpZ28

wow thats interesting.

edcmat-l1

iTrader: (10)

You'll never get the TPS to reset at zero degrees if the voltage is that high. Much over .6 and you can't get it to zero, even if you do the TPS relearn.

99SSragtop

Have you tried ? its obvious its GM's high end of the value and if you had it set to 1.25 volts your idle would be really high.
The TPS has alot of room to play with that small of increment.
First pic is basically resting in an off position sort of speak.Next pic slightly opened and I think that were it would be when you install it because the TPS is bolted down on a slight angle.
By unpluging the TPS with key on for 30 sec and then pluging it back in it resets to zero.
Correct me if I'm wrong.

edcmat-l1

iTrader: (10)

You are not wrong, and yes I've tried. I've tuned oh, at least 2 or 3 of these things. LOL

slow

iTrader: (7)

There is logic and such of what the tps needs to cross for various pcm sources.

What do you get for closed throttle TPS voltage on a stock car? It should be much lower than 1.2 volts (I am assuming around 0.5 or less)

edcmat-l1

iTrader: (10)

Usually very close to .5
give or take a few .01 (hundredths)
No where near a full volt.

99SSragtop

So if you are from .5 to 1.0 +/- or so people should not sweat it as long as there cars idle is within these spec's or what they like it to be at for there own purpose it'll be fine, that's if you don't know and have the tuning programs.

edcmat-l1

iTrader: (10)

For the most part, if you don't tamper with it, and leave you car stock, you have no reason to mess with it.
Now, put a cam in it, and have to raise the idle, then you have some work to do. The biggest thing is to get the computer to realize 0% throttle @ idle.

99SSragtop

LOL but most of us don't know enough to leave things alone. Like me. LOL
My car idle nice with the AC off a few little shakes, but it idles like a Lexus ( super smooth ) with the AC on. I think with the drag on the engine it makes for a perfect 550 rpm SMOOTH idle.

edcmat-l1

iTrader: (10)

Sometimes a little load on the motor will do that. I've done auto cammed cars that idled rough in park, but smoothed out in gear, even though the rpm stayed the same.

99SSragtop

It would be nice to have it idle like it does with the ac on but it doesn't surge,stall,shake so I think I'm fine.

sreve

iTrader: (3)

breaking off the locating tab and sightly rat tail filing the mounting holes
is some times nessasary to get the max to 4.6 volts after a bump stop mod
they sometimes run a high enough voltage to set a code but they do not.
it seems to help a car that runs best at 95% thottle.
things do not always work as designed i have seen rich codes on a vortec 350 with a thottle plate a 1\4 inch thick from coking