The vehicle in question is a 2009 Ford Focus SE with a Duratec 2.0L DOHC engine with 128,000 Km. The symptom is the engine stalls in drive with the engine at idle speed. Whenever you are at a stop sign or a traffic light or a drive thru are all prime candidates to set up for the stall to occur. The engine RPM starts to drop off and then it quits. It only does it when it's near or at operating temp. It has no effect whether the A/C is on or off. It has been going on for 2 months now. It use to stall 1 to 2 times a day in the beginning and for the last month now it's nothing to take a 10 min. drive to the store and have it quit 4 or 5 times before you get home. When placed back into park and turning the key, the engine fires right up and away you go. The car has been well maintained and I have replaced the plugs at 93,000 Km that were purchased from the local Ford dealership. I had it to the dealership when the check engine light finally came on a couple of times when it stalled. There were no DTC's stored in the memory and it passed all tests using the dealerships scan tools. The Mass air flow sensor was substituted with a known good one with no change to the stalling problem. If you never had to stop the vehicle you would never know there is an issue. Any ideas would be much appreciated!