When I run my 1984 22R 4Runner until it heats up, then allow it to cool down rapidly (either through turning it off or significant drop in speed), it has a serious misfiring problem. It hesitates, cannot hold an idle, gains then loses significant amounts of power within a few seconds, and often stalls. This is ONLY after the car has been heated up and then cooled down for a brief moment (0-45 minutes). Other than this, the engine runs great. I already tried replacing the O2 sensor, distributor cap & rotor, battery, and coil. Does anyone have any ideas/suggestions?? Thanks! :confused:

This would probably be pretty hard to troubleshoot. You could start off by monitoring the vacuum when this happens. Perhaps another possibility is something electromagnetic that warms up and when it cools down the windings are separating or opening, like the coil or the magnetic pickup inside the distributor. Strange problem.

it sounds like it might be the idle circut cut off valve.
it's a little solenoid that is screwed into the side of the carb. unscrew it out and take the o-ring off of it and screw it back in.

that is a cheap way to by pass it.

if it still doesn't fix it you can put the o ring back on. it keeps the motor from desieling when you shut it off.
they go out a lot.
i just run them with out the o ring and run my idle real low so it won't diesal.

also have you checked the MC valve? it's under the aircleaner. you just run the motor and put your finger over the inlet and pull the small vacumn line there should be no vac. then put the line back on and you should have momentary vacumn and the motor should idle rough or stall. (straight out of chiltons)