I have a 1994 RX-7.

When the car is in neutral, the car is idling fine at 750rpm.
When I press the clutch in, the car is idling fine to 750rpm.
When I put the car into gear while the clutch is in, the RPM drops to about 500 and sometimes a little below that.
When I pull it out of gear and into neutral with the clutch still pressed in, the car idles fine at 750rpm

I suspected that the clutch is not fully disengaged after pressing the clutch in. I had the car in the air and did not notice the wheels spinning after the clutch was pressed in and put into gear.

The only idea I have is that it was a mechanical issue (clutch plate rubbing against the flywheel was causing the RPM drop). Since I've put that idea to the trash with the example above, could there be an electrical issue? I'm thinking maybe a sensor detecting it is in gear so it tells the ECU to do something differently?

 

Check up above and behind your pedal, little push rod switch isn't broken. Clutch switch.

 

Also, is it difficult to go into gear with the engine running?

 

Could be a bent clutch fork.

thewird

 

Replaced the clutch fluid at a local shop and it sorted out the problem!