Lightly stepped on the gas pedal and checked if the engine will continue to run. If the engine continues to run then the problem is a faulty idle air bypass valve. Fuel injected engine has a device called the idle air bypass valve. This valve is the one responsible in maintaining the engine idle speed if the valve is faulty the engine will stall. By stepping the gas pedal when the engine is about to stall the throttle increases which makes the engine fuel supply enough to run the engine.
If the car will not continue running while you step on the gas pedal then the idle air bypass valve is not the problem, continue the diagnosis and do the following.
Observed if the stalling only occurs when the engine is cold, if this is the case then the problem is the cold start valve. Fuel injection engine also has a part called the cold start valve, the purpose of this valve is to make the engine continue running when the engine is cold by supplying the engine extra gas so that the air/fuel mixture will become rich.
However, if the problem does not only occur when the engine is cold then the problem is a faulty fuel pressure regulator. The purpose of the fuel pressure regulator is to maintain the fuel pressure on each fuel injectors. If the fuel pressure regulator is faulty the engine will get starved with fuel thus making the car stall.
All about car Recommendation
To fix the problem have a mechanic to verify that the idle air bypass valve or the cold start valve or the fuel pressure regulator is faulty, if the mechanic confirmed that one of those parts is the problem then have it replace. If the mechanic tells you to replace other parts, don’t agree just replacing the faulty parts is enough to correct the problem of your Oldsmobile Cutlass that Stalls While Idling.