DIRTYBOYZRACIN

Alright i just did a 22re swap in my 87 pu i tested all the plugs and sensors and my tps is bad but the thing runs good what gives. What exactly does it for

bipolarandproud

A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the throttle valve butterfly.

The sensor is usually a potentiometer, and therefore provides a variable resistance dependent upon the position of the valve (and hence throttle position).The sensor signal is used by the engine control unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

DIRTYBOYZRACIN

Well i fig, the same thing but i wont even measure out on my volt meter it acts completely dead

DIRTYBOYZRACIN

it measures no resistance at all is that possible for it to still be running good

abecedarian

Well you asked what it does:
The TPS serves two purposes:
1) Relays the relative angle of the throttle plate with regards to closed.
2) Signals the throttle is either open or close enough to being closed to be considered closed.
bipolarandproud touched on what happens- the ECU uses the above to calculate other things.
When the TPS signals closed, the ECU drops to default idle settings, ignoring the O2 sensor, and only using coolant / air temp and air flow to calculate timing and air fuel mixture (based on conservative [read as baseline, as in won't hurt the engine] timing / fuel maps).
When the throttle position opens, the ECU looks at how quickly the throttle is opening in order to calculate an 'acceleration enrichment' much like the acceleration pump in a carburetor adds extra fuel when you step on the pedal. When the TPS is at maximum reading, meaning the throttle is wide open, the ECU will also ignore the O2 sensor, relying on a WOT map and adjusting fuel mix and timing based on rpm's, air / coolant temp and air flow. And likewise when the ECU detects the throttle is closing quickly it will cut fuel anticipating an over-rich condition... and if you're on the brakes at the same time, it will cut fuel entirely.

abecedarian

If the TPS tests faulty and the engine is running well, other parameters may have been adjusted to compensate.
The ECU isn't all that dumb- it can calculate timing and fuel mixture based on engine temp, air temp, air flow and feedback from the O2 without feedback from the TPS. It will take what it has to work with and run with it. Consider it an "Intelligent" limp mode.

abecedarian

Are you using http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml as a guide?

abecedarian

Maybe, more importantly, are using an analog meter or an "auto-scaling" DVM?
Not using the proper scale with an analog meter can cause false "faulty" readings.

DIRTYBOYZRACIN

i guess that would have alot to do with why the idle is acting crazy and it seems to run stronger just a little under wot huh? thanks for all the help also i was using a hanyes manual if that makes ne difference

abecedarian

I have an 88 and 91, both 22re and Chilton's and Haynes manuals for each (read as gen 1 and gen 2, so 4 manuals), and neither gives good TPS testing procedures, but I do favor the Chilton's over Haynes- Chilton's has better trouble code information, even better than an most of the sites on the 'net.
Test the TPS according to the link I posted above: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml and let's see what happens.

DIRTYBOYZRACIN

Thanks alot abe ill have to do it tomorrow but ill get back at u thanks again