Sierra stalling

[richies2.0gl]

My 1993 K reg Sierra 2.0 GT (2.0 8v DOHC I4 engine) has a problem with stalling. It happens when decelerating from above 30 mph. It occurs when coming to a stop when the engine is at operating temperature. It does not do it every time but when it does the same fault will re-occur several times afterwards. It will restart immediatley and when started there is sometimes a smell of oil inside the car. I have changed the idle control valve 3 times (using used items) and with each valve the fault occured either more or less often. Other than that the car runs extremely well, uses no oil and sounds very healthy considering the mileage (107k). Any help would be most greatfully appreciated. Richie