1989 Chevy S-10 4.3L V-6. When engine is cold I have to depress gas pedal to get engine to start and have to keep it depressed slightly to keep it running at idle speed or it will stall. Seems to idle a little better after engine warms up to normal operating temperature. Can't engage AC or Defrost when idling or engine will always stall. No Check Engine lights come on at all. Any ideas?