Okay, this problem takes a bit of explaining. When it's cold outside, my 5spd manual likes to rev up on it's own. the colder it is, the worse the problem gets. At it's worst, it's rev'ed itself up to 3800 rpm, while in neutral. When it gets that bad, it also accelerates on it's own. If it's not doing it too badly, I can pump some gas in and it'll settle down, or, oddly enough, I can stomp on the break which will sometimes settle it down. It doesn't really do anything to the car performance wise, it's mainly annoying, as I'm sucking gas, and gas milage is the main reason I bought the car, and it's embarrassing to be sitting at a red light and have my car roaring at 3500.
Also, once in a while, when first started in the cold, it'll die as soon as I put it in gear. I always warm my car up. 10 minutes at least (I live in Wisconsin, it's bloody cold in the winter). If the car doesn't roar up as I was talking about previously, it will start and sit between 1000 and 1500 as it should. This is when the other problem happens. It will idle wonderfully. I get back in the car, pop it in reverse, and as soon as I touch the gas, it dies. I let it roll a bit, put it in first, it dies. The only way to keep it running is to really hit the accelorater, and obviously, at end of my driveway I have to stop. While stopped, I have to keep the clutch half way depressed to keep it running. Once I can get the car into 2nd gear, I'm good, but until then, it dies.
I've had the 02 sensor replaced, as my mechanic thought maybe that was the issue. No luck. He can't think of anything else, and I really don't want to take it to the local dealership to get it checked out. Any ideas?