My problem is this... On a 90+ degree day, with the AC on, and in stop and go traffic, the engine will start to surge. The temperature will get up to 225 or more, and the engine will surge, then rev a little, then go back to normal. After a few minutes, it will surge again. Last week I let it keep doing it in hopes it would throw a check engine code, but it never did (the light does work). In fact it surged to the put that it actually stalled once. Once I got back on the road, and the temperature came down, it ran perfect again. I flushed the coolant and changed the thermostat, the fans all kick on when they are supposed to, so I don't think that is the issue. I have also noticed that when the car is first started, the volts are at 14.5 with the AC on, as the car gets hotter, the volts will sometimes drop to 12.9. To the point that at idle, my turn signals will blink slowly. This is when it will also start the surging. I had the alternator checked, and they said it was fine, although I think the amps are too low at idle. It runs perfect until the temp gets on the high end so something seems flaky. I'm considering the lower temp fan switch, or maybe the idle is too low when hot, any thoughts?