Toyota Repair: 97 Camery Stalling, egr system, camery

Question
Ted,
I have a 1997 Camery, 4cl, w 116k miles.  Here is the problem.  Over the last couple of months it has started to stall or has stalled when coming to a stop.  This usually happens after the car has been running for  20 minutes, so its not a cold engine issue.  The other problem is that this stalling is not consistent.  It sometimes happens only a couple time a week.  When I take it in for service, the car does not stall.  They have cleaned the throtle assembly and replaced the idel speed control.  This has not help. The check engine light does not come on.  

Answer
The most common problem is the idle speed control valve but you said that has already been replaced so we can rule that out, there may be a problem with the EGR system, the EGR valve could be sticking open when the engine comes off cruising speed at which time it should close, if it stays open the engine will run rough and stall. Theoretically, the engine light should come on. Have the egr system tested,it can be done by checking vacuum signals and also by applying vacuum to the valve to see if it is operating properly, you may have to wait until the problem becomes more consistent. One other source of problems with the EGR system is the EGR vacuum switching valve(VSV)it is fairly inexpensive compared to the EGR valve and it may be worth a try to just replace it and see if it helps.
The only other thing may be that there is an intermittent air leak in the intake system.