I have a '91 Geo Prizm with 5 speed 4 cylinder engine. Here lately the car has been let's say studdering usually in 1 or 2 gear but now it does it in 3 and sometimes 4. When the car has warmed up, usually the studdering slows down and when im up to speed the ride is normal and smooth. Got any clues as to what could be the problem.

The heat gave out in my 96 Ford Explorer. Thermostat replacement looks to be too much for me to handle with my small quantity of tools. But, when looking under the hood for mechanical controls, I found what looks like a vacuum line that goes to a contraption (maybe a solenoid) in line with one of the hoses going to the heater core. I see a small lever underneath that can be pivoted 90 degrees in one direction. Could this have something to do with the heat ? I'm wondering if the vacuum line going to the top of this thing , when removed, will call for heat all the time, or the other way around. I understand this will not fix the problem, but at the moment, I just need some heat. I'll look for a permenant fix later. Something else I noticed, with the engine running and the heat on, the A/C compressor was cycling, similar to when it is starving for refrigerant, when the A/C is turned on. In the cab of the vehicle, the heat-a/c selector switch is rotated clock wise for heat. Counter clock wise for cooling, with the off position being in the 12 o'clock position. Why would the compressor even be on when there is no call for cooling ? Could it be that air from the heater coil, is being used to to fight air from the evaporator of the cooling system ? Just for kicks, I removed the dc from the compressor so that it would not cycle. Now I have some heat. It still doesn't feel as warm as I thought it should. With an HVAC analog thermometer stuck into the register, I read 110 degrees. But it sure doesn't feel like it. Maybe cause I was chilled to the bone at the time. And it was checked at mid day. The real test would be at night. Any way, the compressor should be connected to DC but not operate untill cooling is called for, correct ? Some one, help me out. What is going on with these Fords ?