[Schrade]

Originally Posted by Franke

Vettetech1, throttle position sensors are famous for off idle sag. They can be tested with a ohm meter to see if there is a dip in the resistance just as the sensor starts to move off idle. Its a potentiometer and varies the voltage to the ecm.

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edit:
There are NO problems with the engine, no codes, nothing.
There is only the 'off idle sag' / slow response in rpm's.
5V Voltage FROM THE TPS, back to the ECM, is LINEAR; half throttle = approximately 2.3V.
TPS resistance, in mine, is exponential / logarithmic, as snappics show here.
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What's the solution to this? Is it common also in '90?

And do you mean a SPIKE in resistance; not dip??? edit: ain't no SPIKE in mine; it's just VERY LITTLE CHANGE, as the arm swings to midpoint!!! Then it GOES. See snappics below

I give mine SLOW pedal, and rpm's still respond slowly, until it GOES...

Exactly which is the lead to test / procedure?

Alright - I pulled the TPS, and put a multimeter to the signal feed, and signal return pins.

Here are results:

BASELINE



RANGE OF MOTION PEGGED



AT LEAST HALF ROM



This gives at least 1 NEGATIONS...

1) Impedance of MY TPS is not linear (is it broken, and IS supposed to be linear??? )
this could account for the delay in rpm increase with a SLOW pedal

If my TPS IS working, then it is safe to assume that the 5V REFERENCE signal INPUT, FROM the ECM, is inversely exponential, and is calibrated for the non-linear resistance of the internal potentiometer. OR, it is calibrated AFTER the 5V REFERENCE signal RETURNS TO the ECM.