Does your car have the 4cyl. engine? I just replaced the timing belt on mine and found that the exhaust camshaft was out of index. The camshafts on this engine are indexed by placing a strip of barstock in slots cut in the rear of each camshaft. This requires the removal of the valve cover to access. I suspect whoever previously changed the timing belt on my vehicle tried to get away without removing the valve cover and ended up disturbing the position of the camshafts. In any case my vehicle now idles where it should/no more stalling in gear with A/C on. If the engine was ok before the belt was changed, I would suspect the valve timing and recheck camshaft/crankshaft sprocket position.
