Throttle Position Sensor Importance

[jfk1232]

How important is the throttle position sensor? Someone once told me that it is mainly for pollution control. My car has a defective one but doesn't seem to have any major problems running.

[LeSabre97mint]

Originally Posted by jfk1232

How important is the throttle position sensor? Someone once told me that it is mainly for pollution control. My car has a defective one but doesn't seem to have any major problems running.

JFK

How do you know your TPS is defective? If it's not needed, what's telling the computer how far you have your foot into it?

Dan

[Black Lotus]

Not sure what yours does, but I'll tell you what mine does--
*Tell the computer when the throttle is shut--the computer then knows when it can shut the fuel off when the engine is above a certain RPM (when coasting down hill) to save fuel.
The engine idle (IAC valve) is affected.
*Signal to the computer the throttle position by the difference in voltage. The computer has a clock, and if the voltage varies enough between clock cycles it will have the injectors squirt more fuel into the engine (like an accelerator pump). Also, by the voltage, the computer will know when the throttle is over a certain percent open, then will switch over from closed loop to open loop. Spark timing is affected-if it's electronically controlled.
If the sensor craps out, the computer will go into a limp home mode and the check engine light will come on.
Various emission

[jfk1232]

Originally Posted by LeSabre97mint

JFK

How do you know your TPS is defective? If it's not needed, what's telling the computer how far you have your foot into it?

Dan

A computer diagnostic test said the TPS is out. If there's not a TPS, I think the computer uses some sort of default value to allow the car to still run. Even though the TPS is out, the car still seems to run well. The car will sometimes die when I start it, but that's about the only problem I've noticed and I'm not sure the TPS is causing that.

[LeSabre97mint]

Originally Posted by jfk1232

A computer diagnostic test said the TPS is out. If there's not a TPS, I think the computer uses some sort of default value to allow the car to still run. Even though the TPS is out, the car still seems to run well. The car will sometimes die when I start it, but that's about the only problem I've noticed and I'm not sure the TPS is causing that.

JFK

Using a digital volt/ohm meter check out your TPS. Yours may be different that what I have. I have three wires going to it. The gray wire should have 5 volts (with the key on engine off). Next (with the key on engine off) check the voltage between the other two wires. A 91 LeSabre should have around .4 volts with the throttle closed and about 4 volts wide open. Do a search for your vehical on the internet. The TPS (most of them) can be adjusted for the correct closed throttle voltage. Also, with no power to the TPS OHM out the two contacts you checked for the varied voltage. Move the sensor from one end to the other. The numbers on the meter should change with the movement of the TPS. If the numbers goto zero and then back while your in the middle of the range the TPS is junt and should be replaced.


Regards

Dan