Need More Input On Bouncy Idle

[SCT]

Ok, when it warms up, it runs up to 2000 RPM. When it's warm, it drops down to about 1000/1200 RPM... After highway/parkway/whatever/40+MPH driving, occasionally the RPM would bounce from 1000/1200 to 1500/1600 then drop back down after a second and go back up after a second then back down. You'll hear like a click or something, the engine RPM rises, then back down... then repeat. And then it will stop until the engine gets warmer again...

I read somewhere it could be the thermostat and then another that said air in the cooling system. And then another could be the temp sensor.

The temp gauge never went up higher than 3 o'clock position (LE tach cluster).

[REN69]

Temp sensor would also trigger the fan to be ON all the time... so if it's not doing that then that takes the temp sensor out of the question.

Look at your temp gauge when this is happening, if the temperature has gone down a lot when the idle goes up, then it goes warmer when the idle goes down then it most likely is the thermostat. My car was doing this just recently, problem fixed after I replaced the thermostat. Now it only stays high to warm up, then goes down to around 1000-1100 all the time.

[PILOT941]

Its possibly the auxiliary bypass. Not sure what it is but I specifically remember reading about that. Ill send you the link.

http://www.ae92gts.com/ae92gts_quirks.html