What could be causing my vehicle to surge and stall out at idle

Is it completely stock?

Haven't seen a definitive answer for this problem. Lots of people out there have spent big money with no solution. Clean your MAF and maybe replace pre cat OX sensor(s).

Hi guys. I don't mean to argue with success, but a throttle position sensor can't be bad without setting a diagnostic fault code and turning on the Check Engine light. The symptoms you described are a very common result of disconnecting the battery. Until the Engine Computer relearns "minimum throttle", it won't maintain proper idle speed. The additional clue is you usually will not get the nice "idle flare-up" to 1500 rpm for a couple of seconds when you start the engine. Is it possible your mechanic just went out and drove it to do the relearn, but perhaps charged you for the TPS that he tried first? Many of them aren't aware of the conditions that must be met for the relearn to take place, and when they do that without knowing it, they assume the parts they just put in are what solved the problem.