Idle with AC issue
Good day everyone,
So apparently I have something going bad in my engine, as in hopefully a sensor, that affects my idle and the AC.
To start, 96 Tbird with a split-port (03 Mustang 3.8L donation). Runs quite smooth normally. When I have the car in Park or Neutral and turn the air on, it will only briefly cycle the AC clutch (less than two seconds) and leave it off. While doing this, it will decrease the idle speed from the approx 750rpm to about 500rpm or a little less. Of course it goes back up after the clutch makes its cycle. The AC works fine in gear, and this problem had just started maybe two weeks ago now. I just had the idle going crazy on me along with a TPS trouble code, which seems to have been resolved by cleaning the MAF and IAC. I also took off the TPS to make sure that there wasn't a dead spot in it, as in ohm reading through the range increasing for more throttle.
I have also messed around and noticed that if I accelerate the engine to >1500rpm, it will cycle on the AC and drop the rpm to a bit under 1000rpm, but will still go under 500 if I let off the accelerator
I have been trying to look here for a solution, but I haven't really had much luck. The common explanation is that the ECM will readjust for the AC kicking on. That is fine, but I would like to know where the ECM gets its information as to the AC being turned on inside of the car. Obviously, it isn't being communicated well somewhere in the line. I've heard a sensor in the compressor of some cars will tell the ECM to increase rpm for a larger load demand for the AC, but how does it work in the tbird?