I have a 91 lx. My car is struggling to keep an even idle lately. It gets worse when the A/C is on. Theres literally "put put put" coming out of the tailpipe and the car shakes. It seems ok when the rpms are over 1k though. I've also noticed a loss of gas mileage. I'm getting like 20-25 less miles on a tank of gas.

Is this related to distributor problems, wires, bad plugs? somebody mentioned "air boost valve" before but i don't think thats it. Is it something simple?

 

unplug the idle control valve and see if the idle drops, if not it might need to be cleaned or replaced, you might let us know the idle RPM if you can figure that out.
All info helps you get help.
Pull off the plug wires one at a time to see if there is a cylinder missing, no info on the last time plugs were changed.