96 Contour

A little background: I bought the car about a year and a half ago from a transmission shop, which had just rebuilt the transmission, and from the day I bought it, it’s had a rough idle. About 5k miles in the transmission developed a leak which to this day I have not bothered to fix, but I do take care to top off the fluid, and it has performed fine til now. Also, about 4 months ago I replaced the timing belt.

Now the problem: I live in Michigan, and recently, as it’s gotten colder, the amount of shaking it does at idle seems to be greatly increased, to the point where the car will stall from time to time if i don’t keep a little gas to keep the RPM’S up. Right around the same time that this started happening, the transmission has developed some problems. Namely it has trouble shifting from reverse to drive or drive to reverse, and the only way I can get it to shift sometimes is if I give it a little gas.

Otherwise, at any other speed and at warmer temperatures it works fine. I should also mention that the transmission has about 17k miles on it…

So is it a transmission problem or something to do with the Vacuum system/injectors/computer/fuel lines…etc?

Might be reduced/ restricted intake air flow cause by “stuff” buildup. Make sure the air filter is clean. Use a Throttle Body Cleaner to clean the intake, idle air control valve passages, and throttle bore and plate. While in the intake tube, use MAF Cleaner to improve the Mass Air Flow sensor accuracy (hopefully).
Have you changed the spark plugs, and the spark plug wire (if they are aged)?