Two issues, the clutch has two return springs, one external on the linkage and one internal behind the piston.
If the pedal does not return the issue is a master cylinder overhaul or replacement.
Not a good DIY, since you can dump brake fluid on the carpets and paint.
Clutch Master Cylinder Removal/Installation - "Gene M." <firstname.lastname@example.org>
Changing the clutch master cylinder is not an easy job, but it is something a DIYer can do with the proper tools. Most books will recommend that you also change the clutch slave cylinder at the same time (not covered in this). Also remember that the clutch hydraulic system uses brake fluid so protect your carpets and paint and your eyes.
Removal--Under the Hood
Use a turkey baster or equivalent to draw out the brake/clutch fluid from the reservoir until the level is below the fitting on the side of the reservoir that feeds the clutch hydraulic system. I would suggest you change the rubber hose coming off of the reservoir that feeds the clutch hydraulics, so at this point I would remove this hose from the reservoir. (Use the proper replacement, which is currently blue with a fabric mesh sheath on the outside--brake fluid eats up a lot of things and you don't want it to eat up this hose and have to remove the master cylinder again.)
At the tip of the clutch master cylinder there is an 11mm flare nut fitting. Access to this fitting is tough. If you jack up the car you can see it from underneath but the steering and suspension components block your arm from getting a flare nut wrench on it. You need to go in from the top and work in the blind. You should be able to get your left arm down in between the engine and the brake booster and reach around and get to this 11mm flare nut. Expect it to be very tight. Do not try to loosen it with anything other than a good flare nut wrench. Rounding off flare nut fittings on these cars can get expensive because they use a "bubble flare". At this point, use a rag to clean the fitting and loosen this flare fitting (you can remove it and cover the end with a plastic bag and a tie if you are sure you can complete the Under the Dash section).
Removal--Under the Dash.
You first need to remove the kick panel under the steering wheel. It usually has a couple of phillips screws under edge of the dash, one on each side of the steering wheel. There are a couple of other screws (phillips or hex head) a little farther forward toward the edges of the kick panel (around the hood release on one side and in the same area on the other side). Make sure you disconnect the wiring connectors for the seat belt/door chime, and the wire connector and the rubber hose fitting to the climate control sensor. Remove the kick panel out of the area and move the seat all the way back to get enough room to maneuver to get at the clutch master cylinder.
Before disconnecting the master under the dash, I recommend that you disconnect the 11mm flare nut fitting on the end in the engine compartment (see under the hood) because that flare fitting will be on tight and you may not be able to remove it if the master cylinder is flopping around on the inside.
Two 10mm bolts hold the clutch master in place up on a bracket in front and above the clutch pedal. Look up high and by the firewall--they are hard to see and hard to get a socket on them. You need to depress the gas pedal to move that linkage out of the way to get at these bolts from the left side (the nuts on the right side are welded in place). You will need to use a 1/4" drive, 10mm socket with a short extension (75mm) and a hinged handle to get at the front bolt (closest to firewall). The rubber "stop" for the clutch pedal mounted on the firewall restricts access. You can use a ratchet handle on the rear bolt. I don't think there is any way you can get at these bolts with a wrench or 3/8" drive socket. These bolts will be on tight so make sure your socket is fully on these bolts so you do not round off the edges.
The end of the master clutch cylinder that attaches to the clutch pedal is held by a bolt. 13mm and 17mm wrenches are needed to remove the bolt Make a note of which direction the bolt goes in from and which side the master cylinder is mounted to the pedal.
If the under the hood flare nut fitting and the rubber feed line on the fluid reservoir were removed, the clutch master can now be pulled out. (If you are not planning on replacing the rubber feed line, you may want to remove the plastic fitting on top of the master cylinder but I think you will find that it isn't easy to do this working in the cramped area). You may need to loosen (not remove) the bracket that holds the switch in to disengage the cruise control for the clutch pedal so that it can be swung out of the way to get room to slide out the master cylinder. A 10mm open end wrench is needed and the nut to loosen is on the brake pedal side. Be sure to have rags down on the floor to catch any fluid that drips (brake fluid bleaches out carpets and corrodes metal).
I would recommend that you get a new plastic fitting for the top of the master cylinder and have it around even if you are not replacing the feed hose in case the old one breaks.
Installation--Under the Dash
I don't know if it is needed, but I "prime" the new master cylinder by putting some brake fluid into the feed side to get some lubrication on the seals. Put on the new plastic fitting and attach the feed line--put a plug in the other end of the feed line so that you don't get debris when running it through the firewall. Loosen the end plug so that when you are working back under the hood you can easily get it off but leave it on so that you don't get debris when running it through the firewall.
Loosely rebolt the master cylinder in place. Make sure the end is on the correct side of the pedal before you start threading in those 10mm bolts and make sure you are not cross-threading them. I tend to use a bit of non-hardening grease on the large bolt that attaches to the pedal to make sure the plunger can freely move on the bolt. Don't tighten everything all the way because a little "play" may help reconnect that 11mm flare nut fitting under the hood.
Installation--Under the Hood
At this point I reconnect the 11 mm flare nut fitting on the end of the master cylinder. This can be very difficult working with the left hand in the "blind" because the hard pipe may not give you the proper angle to get the threads started. If you are not straight on, you won't be able to get this back on and will rub your fingertips off. I have recently started to disconnect the 11mm flare fitting that is at the bottom of the metal pipe going down to the clutch slave cylinder to make the other connection at the end of the master cylinder less frustrating. This involves jacking up the car to get at this lower fitting (again make sure to thoroughly clean the area before opening hydraulic lines and keep your face away because you will get fluid dripping when you disconnect), lowering the car and attaching at the master cylinder, jacking back up and reattaching the lower fitting.
Reattach the feed line to the reservoir making sure your line is not kinked both under the dash and under the hood. If your car didn't use one, you may want to use a hose clamp or zip tie to hold this feed line in place--especially if you pressure bleed your clutch or brake lines.
Installation--Back under the Dash
Now tighten up the 10 mm and the 13mm/17mm bolts. After you have replaced the clutch slave cylinder (if applicable) and have refilled and bled the hydraulic system and you know the clutch is working, double check for leaks under the dash before reinstalling the kick panel. Remember to reconnect the wire connector and rubber hose to the climate control sensor.