I'm having a surging problem, i replaced the IAC recently, so thats fine, bad TPS maybe? It's more noticable at night because the lights dim/flicker when it surges and the voltage gauge moves. Basically, when I left off the gas, the rpm's come down a bit quick, so it surges to keep it above 500 rpm it looks like, so it doesnt die. Same thing goes when I rev it, or keep it at 3k rpm's and left off, it'll sky rocket down and surge, it doesn't do this when it's cold, but it's only cold for what like 5-10 mins till it fully warms up. Also, some idiot put a hitch on the car I had removed, the wiring is still there, it has a box inside the drivers side rear comparment, and a box under my diagnostic link, with like a lever to adjust something. Basically I'm wondering if it's taking more voltage, even if a trailer isn't hooked up to it, seems to take a volt or 2 with just the brakes applied.

nobody?

The volt gauge dropping is because when its surging the alternator is not turning as fast as it needs to. Therefore the volt gauge is registering the change in volts as the alternator turns and slows down and climbs back to specs. Its because the car is dying almost like when starting the car i guess. Kinda hard to explain but yeah its just cuz of the motor not turning the alt fast enough. Surging. I would check fuel pressure first. This same exact thing happened to me and the pump wasnt puttin out enough. Ended up being the hose connecting the pump to the sending unit. But yeah get a fuel pressure gauge and test your pressure.

are u selling the alt cause of the surging?

Nope, and this issue has been resolved awhile ago.

I upgraded my alt from 105 to 140 and the wiring from alt to battery as well as the TPS sensor, and all is well.

The 140 alt I'm selling is pefectly fine, infact I've had it tested, I'm just upgrading to support a massive amp and high RMS subs, so I need the 200 amp which holds 120 amps at idle, so my lights don't dim when 2000 watts hits the subs.