When idling the engine randomly revs from 800 RPM to about 1,600 RPMs?

This happens when it is in gear at a stoplight and requires me to throw the transmission in neutral (and then back in gear when the light turns green) or put my foot firmly on the brake while the engine strains against the transmission trying to move the car forward. Recently we replaced all four spark plugs and the ignition coil assembly. Last year the BCM was replaced. This engine idle speed issue is relatively recent, prior to the ignition coil replacement. At that time the engine was running rough. It accelerates smoothly and when the idle runs up and down the engine is smooth. Throttle body problem? Mass air sensor? Vacuum hose leak?