This happens atleast once a month to me.
I would drive normal, then all of a sudden the engine just revs to 3k and stays there. You step on the gas pedal, the rpms goes up and when you release it drops back to 3k and you can hear it backfiring once it goes back to 3k.

After a while it stops and everything is normal again......im confused on this.

 

is it cold when it does this?

 

its at normal temp

 

RX7s have a pre idle switch (dont know the technical name for it) and it is located at the bottom of your radiator...this may be what is causing the high RPMs...if that isnt the problem...recommend checking your TPS

 

check tension on cruise control and throttle cable. I've had a similar problem before and it was the tension on the cruise cable

 

check the thermowax.. maby bad thermowax. ? or something? with the TB.. becuase i know when i removed my Thermowax, it got stuck open at 3k also.. but that was before i removed the butterfly's and shaft..

 

I have a feeling that the AWS is stuck, shorting, or the wiring otherwise has a problem. Somehow it's getting 12V when it should not be or is physically sticking open.

 

I dont have cruise control so thats out. I did check the throttle cable though, its not tight or loose, its just right.

How you check for bad thermowax? I know the thermowax opens up the tb at cold start to rev at 3k and it control the idle at coldstart.
The AWS is the accellerated warm up system right?

 

It likely will not be the thermowax. It is responsible for the 1500RPM thermowax and when it fails you will get an idle between 750 RPM and 1500 RPM.

The AWS solenoid is used during the accelerated warmup and it opens up when the power steering generates load.