Mitsubishi Colt engine cutting out

I am having problems with my car engine dying. It tends to happen when I am slowing up to a junction, stopped at traffic lights, slowing to come around a corner or going up a very slight incline. The revs just drop to under 1 and then the engine light comes and it dies. I can sometimes start the engine immediately, but other times it takes a good few attempts. When I do get the car going again the revs shoot up to over 2 and then other times it stutters and slowly creeps up to over 1. If I am in first gear waiting to go somewhere im finding myself pressing the gas pedal to keep the revs above 1 to try and stop the revs plummeting. Have had the spark plugs and leads changed to no avail. Heard that it could be the idle air control or the throttle body ? Please help thanks!