I had this problem in my 1993 Saturn SL2. It is probably the fuel injectors. No matter how many cleaners you run through it, you need to take in and get the injectors flushed out. Probably about $70. My car went from dieing about 10 times a trip, to none.
The idle is controls ONLY by the PCM. Replace your ECTS along with cleaning the Idle Air Control valve located on the throttle body.
Could be throttle plate stuck open Try to free it with screwdriver with engine off
Posssibly the idle is too high. TAke the idle solonoid off of the throtle body and clean it.
Idle is computer controlled by the pcm (computer)-not adjustable.
Is it a stick shift?
Most cars typically idle between 400 to 1000 rpm
check your fuel bypass or fuel regulater
I would check for a vacuum leak first, then the idle solenoid which is located on the side of the intake plenum.
Idle speed control or Idle air control.
Does it miss on acceleration or at idle? If on accel I would be looking at the plugs and wires
Either the throttle plate is sticking or the idle air control is not responding to ecm signal.
Idle is computer controlled and can NOT be adjusted.