hey...let me ask you..I have a 84 rx7can't seem to get the R.P.M down to 750 or 850 what ever.. it has a/c any idea's...Thanks

 

not to state the obvious, but you've been turning the Idle screw, right?

 

I had a similar problem once, and it turned out to be a vacuum leak...

the anti-afterburn hose was what got me (it's about a 3/8"-1/2" rubber line on the rear passenger side of the engine going from around the carb to the lower part of the intake manifold) damn thing is right near the exhaust manifold and there was a hole in it that I'd describe as HUGE..., because the hole was so large I couldnt' hear it like you would a smaller one...

I found it with a little carb/injector cleaner...

 

pull the rats nest.

my engine runs rock smooth at 400 rpms. sounds tight as hell.

I got it set rich as ****.

 

Spray starting fluid on all the vacuum lines to check for a vacuum leak...if the rpms increase, you've found the leak. Even a pinhole can be problematic. Otherwise, make sure the timing is set correctly and adjust the idle speed and a/f screw accordingly.