Shutting off, running horrible, fluxuating RPM, yet no codes

My first suspect for the fluctuating idle speed (Hunting) would be a bad IAC (Idle Air Control) valve. Unplug it and start the engine. The check engine light will come on, ignore it. You should have a very low, but steady idle. If you do, replace the IAC. How long was the vehicle in storage? Was it stored in a garage or outside? Was the gas tank full when you parked it? Did you disconnect the negative battery cable when you parked it or did the battery go dead while in storage? If the vehicle was stored outside check for rodent damage. Mice, squirrels, and rats love to chew on wires and vacuum hoses! The gas tank should have been full when you parked the vehicle. If not you can get water condensation in the gas tank. Put a bottle of Drygas or similar product in the gas tank and fill it up. On some newer vehicles the computers must be powered up at all times, no matter what. If yours is like that, your owner's manual should tell you, and you disconnected the battery or the battery went dead in storage the computers must be flashed (reprogrammed) for the vehicle to run correctly again. Look in the owner's manual for the proper procedure when storing the vehicle. If that's the case you need to go back to the Dealer for a flash. Hope that helps! Jim

It was stored inside a warehouse, tried the IAC, no reaction change. Battery was totally disconnected for the 6 months it has sat, and it is no issue. Gas was filled and had stabil in it, and yes have even drained some gas at filter, looks perfect. When it rains or is wet from condensation it runs perfect. As long as you're flooring it or "hot rodding it" it can run fine. If you let the vehicle either ease up to 1500 RPM or if you're slowing and it passes through the 1500 RPM area the vehicle goes crazy. either dropping without reason the RPM to the point it may stall or definitely downshifting, or it just may depend on how fast you're driving, it just may stay at that speed for minutes at a time. I have had it go as much as 1.5 miles without my foot on gas. Yesterday while it was being test driven, every time the mechanic would turn the wheel to about 2 o'clock while slowing down it would shut off. His scanner said it just "shut off" for no reason whatsoever, and never left a code. He did it 5x in the parking lot.

That sounds like a problem in the steering column. Don't forget the ignition system runs through the ignition switch which is in the steering column. Maybe some corrosion happened when it was parked and now you have a bad connection. There's also a pressure switch in the power steering system. When you turn the wheel and the pressure in the power steering system increases the switch is supposed to send a signal to the computer to speed up the idle to prevent stalling. It's possible the switch is sticking. Hope that helps! Jim