when i switch on the ac the idle rpm go up some time to 1100 and drop to 800 ( this is when the compressor is working)after a few seconds,when the ac compressor clutch switch off the rpm go to 100 rev a moment, or the engine shut off some time.
when i switch off the airco the engine runs normal 500-600 rev‘s ,also when the car is not in gear it works fine, when the compressor switch on the rpm go to 800 and when the comp. swich off it go to 600 rev.
over here in the Netherlands the lexus dealer have no idee how to fix it.
Please help.
Bennie

 

Bennie, some fluctuations of RPM is absolutely normal
When A/C clutch engages, there is an extra load on the engine. The RPMs drop momentarily, but ECU (Engine Control Unit) sences it and increases RPMs before you can even notice the drop. This increase in RPM is due to ECU compensating for the additional load.
The fact that your RPM drops to 100 or sometimes to 0, tells me that your TPS (Throttle Position Sensor) or your ECU might be mulfunctioning.
Start with TPS - it's a much cheaper fix.
Good luck.

 

I have fix the ac/idle problem to my car, i just clean and lubricate the idle control valve, on the axel and the valve was a little carbon.
b.t.w its a 94 with 140k mile.