I am new to the RX-7. On my '85 GS 12A, once the engine is at operating temperature (~190F), the engine stumbles a little when coming off idle, going thru about 2k. Above that it runs great. The idle seems good, around 800 rpm. It looks like it idles smooth, it does shake a little at idle (compared to my 98 Dodge Ram with a 360), but not enough to feel in the car. When leaving a stop, it stumbles sometimes enough to make the engine die. If you rev it up to 2.5k while letting the clutch out, it runs fine (usually even gives you a little tire chirp). I have done some basic vacuum system inspection visually and with carb cleaner. The plugs and wires are new. The car has been sitting (and driven avery few weeks) for about 2 years. I have tried spray in carb cleaner and fuel tank carb cleaner. It seems to be getting a little better, but still needs help. Any suggestions?

 

Either your accelerator pump is shot or your idle mixture is set way too lean.

To check the accelerator pump work the throttle by hand and look down the carb throats. You should see a nice big squirt of fuel into both primary barrels. If not than you probably need to replace the accelerator pump diaphragm and/or clean and maybe rebuild the carby.

To set the idle mixture first turn the screw anti-clockwise a few turns to start off. Then turn the screw clockwise until the engine just starts runing rough and then back out about 1/2 a turn.