I would remove and clean the IAC (idle air control) and the bore that it rides in. It is held in place with two small screws, and you can get at them but they are a little difficult to reach. The IAC is mounted on the throttle body, near where the big rubber air hose connects. Clean off all the black crap on the end of the "pintle" of the valve, and using a small rag sprayed with carb cleaner, clean out the bore where it mounts. Take the o-ring off the IAC and clean it with soap and water and re-install.
On my '92 you need to disconnect the electrical connection to the throttle sensor to make room for removing the IAC.
The IAC is what controls your idle speed. The computer directs the pintle to move in or out, allowing different amounts of air into the throttle body. They usually get all black with carbon after a while. Sometimes they need to be replaced.
When you have the A/C on, the computer tries to set a higher idle speed, and this is why it runs better with the A/C on.
1992 green ssei. Tan leather, moonroof, power everything. 161k miles
Goodyear RSA Plus 225/60/16 VR on chromed factory crosslace rims. McGard chrome lugs.
Audio system: CD player w/equalizer, subwoofer (all stock).
Delco premium wires, NGK TR55 plugs, K&N stock style air filter. Ceramic brake pads. New rear brake tubing and proportioning valves. New wheel cylinders, front rotors and calipers. New front wheel bearings. Replaced crank sensor and harmonic balancer. Rebuilt instrument cluster. Cleaned A/C evaporator. Valve cover gaskets. Alternator. Front stabilizer links. Replaced all power steering lines and transmission lines. Cleaned MAF and IAC. New door appliques. Rebuilt steering gear. CERAMIC brake pads, I love them. I am listing all this in case someone needs advice on any of these repairs.