Volvo Repair: fuel pimp sensor, intake valves, mind reader

Question
where is the sensor located? To me it looks like a big fuss.  My car started to cut off if I stayed at a light too long.  It would crank right up and run. A mechanic said he cleaned my intake valves.  Then the car would cut off riding down the road.  It would take a couple of minutes to start.  Now it wont stay started.

Answer
   Brenda, I would like to help you but I need some basic information first. As much as I'd like to be, I am "not" a mind reader. Make, Model, Year, Mileage and any past history would be helpful.
   By the way, what's a "fuel pimp"? Someone that sells black market petrol? VBG

Mark