92 Lexus sc400 When first starts runs fine but high idle around 1200 rpm. As soon as it starts to warm up then idle continually up and down between 1200 and 1800 rpm. Took out and cleaned the IACV. While idle is going up and down can unplug IACV and NO difference also can unplug the TPS (farthest away from the block) and NO difference. But while it is acting up unplug the TPS (closest to the block) and just goes back to 1200 rpm and stays steady. Is this TPS my problem? Don't want to buy one if its not. And why is it now running so high on rpm's. NOTHING has been adjusted was running great before this problem! ANY ADVICE FROM SOMEONE WHO KNOWS!!!!

Look over all your vaccum, test your coolant temperature sensor that goes to the ECu not the gauge one. HOws your throttle cable? sticky?

mileage of vehicle? any tune up done? help us figure out sources of issues.

No vacuum leaks, Throttle cable not sticky at all, 140000 miles, no recent tune ups. What do you think about the TPS issue? Think that might be the cause of the problems?

Can anyone help with this problem??

If you loosen the screws on your tps and turn it while it is running can you hear the rpm's pick up or drop off. Sounds like a tps issue to me.

Any more Ideas before I go buy a new TPS?

Try calibrating your current one first. Not trying to toot my own horn, but I did a write up about hesitation issues and I included the calibration procedure in there.

https://www.clublexus.com/forums/sc-...on-issues.html

I would say your TPS..

Was your IAC valve real dirty or have alot of carbon build up? Check for vaccum leaks with carb cleaner or WD-40.