My daughters Alero (4cyl 2.4, 178,000 miles) also had the same problem. Would stall coming to a stop or when coasting. Rough idle and stumble or stall, sometimes both if you put the slightest pressure on the accelerator when stopped in gear. No check engine light.I eliminated the obvious.I cleaned the throttle plate/housing (very dirty). Had fairly new spark plugs. Replaced the spark plug boots/connectors and fuel filter (original filter!). But still had same problem. Then I saw it! When the engine was at idle the vacuum was sucking the hose to the map sensor closed! Replaced with $2.00 peice of vacuum hose. Problem gone. Still has inherent shaky idle but runs good. Im happy. And solved the problem myself. Sometimes the vacuum hose looks fine at the sensor but is split where it connects to the vacuum port on the other side.
Saturday, September 1st, 2012 AT 8:46 PM