Chrysler Repair: 1999 Chrysler Sebrin: Stall when slowing, screwdriver blade, penetrating lubricant

Question
Our car runs great most of the time.  It randomly stalls when stopped or slow down.  We have replaced plugs, wires, distributor, rotor and it started up again and no problem is detected by the computer.  Dealer left it running all day and no stalling occurred.  Do you know of anything else that may be causing the problem?  Others have tried different sensors but none have helped.  One guy reported a new gas cap did the trick, could it be that easy?  Please help it is annoying.

Thanks,  

Answer
Hi Kelcy,
One often over-looked item is called the egr valve which is a pollution control device that sends exhaust gas back to the intake manifold when running at speed but which is supposed to close by spring-action when you take your foot off the gas and come to a stop. If it hangs up slightly ajar the engine will stall or stop because the exhaust gas dilutes the mixture too much. You can check this yourself and lubricate the valve so it closes fully by spring-action.
It is located along a pipe that runs from the left exhaust manifold (on the side of the engine facing the front of the car) to the intake manifold area (where the incoming air in the large rubber tube enters the throttle). That valve is metal and has a round fitting with a vacuum hose attached, mounted on the top of the valve, and the round part is attached to the main body of the valve by a sort of saddle.  Inside the open saddle you will see a metal rod (with a slot) that connects the round top fitting to to the valve body. That rod is a stem on the valve and it is supposed to go in and out in response to the engine vacuum which varies with RPM and throttle opening (gas pedal position). Take a spray can of WD-40 or other penetrating lubricant and spray the stem where it enters the valve body and then use a regular screwdriver blade tip inserted in the slot to lever the valve in and out to try and free up its motion. Also check all the rubber vacuum hoses associated with the valve and a nearby vacuum solenoid valve. If the valve seems to open (against the action of a spring) and close firmly by the spring action when using the screwdriver blade to facilitate the motion, then you will have cleared that possible cause of the stall. You can, once it is idling, check that the valve stem moves when you rev the engine from idle to 2500 rpm and back to idle just be observation.
Roland