960 1993 177K miles. Intermittent rough idle.

Unlike the 740 series, the 960 TPS switch does not have a positive click. I think it acts more like a potentiometer. At what point in the TB butterfly travel does the IAC valve cease to control the car's idle.

I ask because I think I have an intermittent IAC valve, but I don't know the best way to test it. I have cleaned the valve part several times, including dis-assembly and armature cleaning. Both coils measure 13-15 ohms.

The question is, how do I know it is opening the correct amount. Can I apply 12vdc should and should the valve open all the way. With the iginition key turned on (not started)the valve hums. Using a stick I can move and vary the valve opening by about 1/8". When I remove the stick the opening DOES NOT snap back.

Here is a few tests to run for an IAC valve.

Looking at the 3 connector pins on the valve. With the pins going left to right, on the outer edge, one side has two guides on the ends and the opposite side has one in the middle. With the side with two guides up, pin 1 in on the right.

With an ohm guage pins 3 and 2 should read 10-14 ohms. Pins 1 and 3 should read 26 ohms at 20 degrees celsius.

Twist the valve back and forth, one should feel or hear the slide striking it's limits.

This is per my fault tracing manual, one thing I discovered, is sometimes the references to the pin locations are backwards. Just keep that in mind if things are not reading correctly.

DanR 94 964 279,000 miles (45,000 on the new engine)
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DanR

The TPS is a dual pole switch: continuity at both extremes, nothing in the middle. It signals both "idle" (for IAC operation) and "WOT". In between, the absence of continuity tells the ECU to shut down the IAC. You can easily test it with a multimeter set on "continuity": the middle connector is ground.

Your IAC is spring loaded and should return to zero when you rotate the inner valve. It is a stepper motor.