1987 944 clutch pedal stays on the floor

The clutch being on the floor says the slave cylender, or pilot bearing for the clutch is faulty. The vehicle should still start if you put it in neutral, it just can't be driven. Unsure about the windows.

The clutch is not adjustable it is fully hydraulic. That means it is self adjusting, if the clutch pedal engages high on the pedal and the clutch is hard to push you need a new clutch plate and pressure plate.

If it's cable actuated clutch, the cable may have snapped, which is also indicated by the clutch pedal dropping to the floor or becomes lighter to press. Check at the transmission bell housing, the clutch lever may have been broken or bent. If it uses hydraulic system, the slave pump may have been dislocated, at the transmission side.

engaging?
you meant dis-engage im sure.
pedal up is engaged,
pedal at floor dis-engages it.
my guess, is the clutch drags unless i push the clutch pedal 100%
to the floor.
1: bad cable is 90% cause. non last this long.
2: no free play is way too loose.
3: broken lever on the pedal top. caused by #1

all fail modes covered here.
http://www.fixkick.com/tranny/clutch/clutch-on-kick.html

Well, it would shift easily with engine off, because the transmission input shaft is not turning. Engine running and clutch engaging good, the input shaft would again be stationary and allow smooth shifting.
What you have to determine is if the clutch disc or pressure plate is bad (a new clutch is needed), or if the pedal hydraulic system has a malfunction. When you push the pedal down, a rod from the top of pedal pushes into the clutch master cylinder bolted to the firewall under the hood. This cylinder has a reservoir filled with brake fluid. When the rod forces fluid from the clutch master down a steel line and into the clutch slave cylinder down on the transmission bell housing, the hydraulic pressure forces a plunger from the slave cylinder to extend and push the clutch fork lever a small amount, enough to force the clutch release bearing (aka throw-out bearing) against the pressure plate. This relieves pressure on the clutch disc and input shaft becomes stationary for easy shifting.

I had this same problem the cable is fine its a clip on outer cable to stop it mooving when you press clutch mine poped when I tightened the clutch cable still don't have solution though waiting to payday to take it to garage

on the transmission there is a slave cylinder that works like a brake cylinder, when you apply pressure to the clutch pedal a rod inside the vehicle under the dash pushes into a clutch master cylinder, (almost like a brake master cylinder without the reservoir, as the clutch master cylinder works off the brake master cylinders reservoir) the plunger in the clutch master cylinder applies fluid pressure to the slave cylinder,(located down on the trans near the clutch fork assembly) which projects a piston rod into the clutch fork dis-engaging the clutch. To bleed the clutch slave cylinder locate the bleeder screw on the slave cylinder,break loose so it loosens and tightens easily. Check fluid in brake master cylinder reservoir,fill if needed, while bleeder on the slave cyl is closed have a helper push clutch pedal to floor and back 7-8 times, (At first the clutch might stay at the floor, just pull it up by hand or foot and continue) after several pumps with no rest time push pedal to the floor and hold down with foot pressure, at this time loosen the bleeder on slave untill fluid leaks out, watch for air bubbles, close bleeder and repeat untill there is no sign of air bubbles, (make sure to check fluid in the brake master cylinder and keep fill as needed, do not let fluid get less than 1/2 empty as it might **** air and you will have to start over) If this does not bring clutch to operate then you need to check if slave cylinder is reachig its full extension of push rod or not. If it is not then you will have to replace the clutch master cyl or the clutch slave cyl or both as seals are bad and wont hold pressure. Or you need to inspect the clutch fork,the throw-out bearing, or the pressure plate fingers and clutch plate for failure or broken bent parts. I hope it turns out to be a easy fix on that clutching thing.

YOU DO NEED A NEW DISC AND MOST LIKELY A MASTER AND SLAVE HYDRAULIC CLUTCH CYLINDERS, THE STICKING MAY BE DUE TO OVER TRAVEL DUE TO THE WORN OUT DISK.

Your Friction disk (clutch) is worn out. Have it replaced....might also need pressure plate, but not necessarily.

believe it or not, the floormat on my 2000 Sunfire will sometimes slip forward and hold the clutch pedal down against the floor. It truly feels like a mechanical problem, but simply pull the floormat away and the pedal pops right back up!