i would say that if the plugs fire that the ecm is good. metros are notorious for being very sensitive to a worn timing belt. the belt can appear to not be worn, but if it has streatched longer and ofsets the cam by as little as 3 degrees, then the engine will not start, but the starting fluid has more power than regular gasoline fuel and will run the engine. try changing the belt. a hint on that.... unless you want to pull the engine, you will have to make a slit in the bottom of the timing cover with a razor knife so that you can pull it off and see the timing marks. the timing marks are 4 spurs sticking out of the crankshaft behind the main pulley and then a mark on the cam sprocket will line up with a grove on the valve cover.