I have a third gen box, stock PS pump and a hydroboost. Recently I've noticed that at times my engine RPM will start to oscillate. I thought that maybe my fuel injection setup was wigging out or something.
Anywho yesterday I disabled the IAC motor (the ECU opens and closes this to let more or less air in at idle) and timing so all the ECU could do was inject fuel. The RPM still fluctuated?? I removed the alternator belt thinking that maybe the alternator was loading/unloading the engine, but still had the same issue.
I noticed that when I hit the brakes hard or turned the steering wheel all the way that the engine RPM would fluctuate. I checked the fluid level and that's good as well as the belt tension, but it seems as though the PS pump is loading and unloading the engine. The pump will squeal a little and the RPM will drop, then the pump must unload and then the RPM comes back up, then I get a little quiet squeal again and RPM drops, repeat. Brakes and steering seem to work fine though.
Anybody ever experience the PS pump loading and then unloading the engine causing RPM fluctuation? Personally I don't think that I've ever had it happen. I know in the past that if I turned the wheel all the way one way or the other the PS pump would load the motor and the RPM would drop some, but I don't remember ever having it load/unload causing the RPM to fluctuate.