My GGSX will start normally and run for up to 10 seconds and then it will shut off, kind of like if I were to turn the key off. The engine DOESN'T sputter shake or anything it just shuts off. When it dies the three dash lights come on (check engine, brake, oil light) because the car is still in the "on" position. My first instinct is alternator or fuel pump, but the symptoms of those going out would have the engine shake and stutter before dying. Then also the car wouldn't start right back up if the alternator was shot.
I can start the car right away after it dies but it will die instantly after. I can also put the car in gear and run it but as soon as I'm off the gas it will die. If I hold the throttle almost wide open it will not die, but under low throttle it will still die.
After some research I have a feeling that the IAC has gave out on me because the idle would be very sporadic, before the dying issue started. While it was in its warm up cycle it would rev to about 2000 then drop to around 1500 then drop and repeat over and over until the car was at operating temperature then the idle would be fine and smooth at around 1000. It's just I have no idea how a car reacts to having the IAC go out, and that's where my questions start.
What is wrong with my car?
Where do I even start to diagnose this problem?
How does a car react to the IAC going bad?