Hyundai Repair: 2000 Elantra 4 cylinder, charcoal canister, scan tool

Question
I pulled into my driveway 10 days ago and the check engine light went on and the car started bucking. I had the car towed into the dealership. They told me I needed new plugs and wires & also  cleaned the fuel injectors.
I had the work done. The car had much more power, the check engine light is off but the car is now randomly stalling, usually after I have been driving about 20 minutes and am stopped at a red light. It starts to idle rough then there is an extra tremor in the engine and then just simply stops. It starts back up immediately. I called the dealership, brought the car back in and was told they could not duplicate the problem but "keep them in the loop". I drove it to work this morning and lo & behold it stalled...Any suggestions?
By the way I appreciate your help...

Molly

Answer
These types of issues are difficult to diagnose because any tests run while the problem is not occurring will almost always show good results.  If you haven't offered or requested to have the dealer's technician take the vehicle overnight for a day or two in an attempt to duplicate the condition, you may wish to start there.  Even though he won't be likely to be able to do a good diagnosis on the road, he'll at least be able to feel it occur, which can be extremely useful in knowing what type of issue it may be.

As it stands, the problem could be just about anywhere.  I'm hoping the dealer at least installed the scan tool and checked to see whether there were any engine or transmission trouble codes.  

The only thing that comes to mind is that the situation you describe is about the correct condition for your car to be testing the evaporative system.  I've seen one or two Elantras stall somewhat randomly when the purge control valve opened because the charcoal canister was full of fuel.  When the valve opened, it caused so much fuel to be sucked into the engine that the engine flooded and stalled.  In these cases, there was a defective check valve that allowed the fuel to leave the fuel tank and enter the charcoal canister.  This is an idea, but I don't hold significant hope that it's the cause of your issue.  The only vehicles on which I've seen this occur are newer than yours with some of the evaporative system parts being significantly different.