How did you determine proper voltage from the ECT? The reason I ask is nothing to do with the ECT, really, but your method of reading voltage, if done at the ECU with the plug hood removed is the best way, and not part of the standard repair-manual methods.

If you can apply that same technique to the TPS signal at ECU pin 2, you can check more certainly that "click" you hear when the throttle closes is really being seen by the computer. Easy work, just backprobe pin 2 with your voltmeter, and stretch your left foot to the gas pedal to see it goes from +5V to ground solidly and consistently each time you back off the pedal.

If the TPS is confirmed good, the next place to look is in the idle control valve. Look for sticky blowby deposits and sludge. Check the connector for corrosion. This bit of crud caused surging idle on an older, LH2.2 car.