clutch problem
 

My clutch is refusing to completely return after each shift. It is disengaging, just staying about halfway up each time. I can pop it back up all of the way with my foot. This seems to have started about the time the temperature dropped a few weeks ago. The problem subsides after 20-30 minutes of driving. By the time I got to work this morning it was working fine.
Could this be a broken or missing spring? The master cylinder?

Master or slave I would bet. And the best bet is to replace both at the same time.

Are you losing brake fluid--brake fluid reservoir getting low?

If yes, then you have an external hydraulic fluid leak. If you don't see any brake fluid on the driveway then check on and under the carpet below the clutch pedal. That's where my master cylinder was leaking it's fluid.

If you don't see any brake fluid level drop then you might have an internal master cylinder fluid leak. The fluid is bypassing one of the internal seals and not holding pressure.

Check out the clutch pedal drawing at http://www.pelicanparts.com/944/944_parts/944_83-85/Pic52.jpg
It there is a spring. Make sure it's attached and not weak. Although, a spring weak/missing spring alone shouldn't cause the problem you are having.

I agree with Scott. Change the master and slave at the same time. I didn't, and the slave started leaking 6 months after I changed the master.

I just went throught the EXACT same problem, except my clutch starting flattening out to the floor. I had to poull it up by hand. Id your brake warning light on as well? check you brake fluid. If it is down fill 'er up and I bet after pumping the pedal it will come back.
I had a bad Master cylinder. It had done the same thing 2 1.2 years agoa when it was replaced then. My Slave had to be replaced 1 1/2 years ago.