My son say his Century quits running after awhile when he puts it in park or reverse, runs rough then quits. He can start up it right away again. I told him to put a bottle of fuel injector cleaner in the tank. Any other ideas why it does this? He also said that when starting it cold it idles high! Is this normal? Thanks

Try to unplug the EGR valve. Don't forget to cap the vacuum line that you unplug from the valve.

A high idle could be the result of a vacuum leak under the throttle body, and will affect the ability of the ECM to properly control the idle, which could lead to stalling. The idle air control, or IAC operates with a stepper motor, which requires some time to reach a correct opening. If the mixture is erratic, the resulting lag could cause a rough idle or stalling. The EGR could also cause this condition if it sticks open. These vehicles were known for both conditions. One other condition which could lead to a similar condition is a situation where the solenoid controlling the torque convertor clutch can stick, dragging the engine to a stop, and causing stalling on gear engagement, similar to trying to engage gears without engaging the clutch. Ray