Okay so I have a 2000 GT with roughly 156,000mi on it. It is currently -12F and I'm not sure if that is playing a part in this or not. It starts and generally idles fine to begin with. Then yesterday I was driving around and when I let off the gas to coast to a stop sign the engine stopped. I shifted into neutral and did a rolling start and put it back into gear after I stopped. Not that big of a deal but that wasn't the last time it did that. It seems to be fine and then after a couple minutes of driving instead of being at about 1000rpms when I'm sitting at a stop light it will be around 500 and then it will go between 500-800 and then kill itself. It also tends to do this when I let off the gas as well. It will start fine after it stalls. There is no miss as I am driving down the road or accelerating.
The car is pretty much stock. Just added a home made intake, replaced MAF sensor, and did an oil change from the 5w-30 I accidently put in last oil change back to the 10w-30. Not really sure what is going on and I kind of have to drive the car and with it being -12 I figure if I break down I may be in trouble pretty quick with how cold it is so I would like to try to get this solved as quickly as possible. Thanks in advance!