1991 cadillac devile won't engage in gear.

if its manual and you literally cannot pull the gear shifter out of gear, then when the engine is off, take off the parking brake, have someone rock the vehical back and forth gently while you keep the clutch depressed and try to take it out. then it should be towed (still in neutral might i add) to a shop. if this does not work with the clutch depressed, give it a shot with the clutch engaged (pedal all the way up)

Had exact same problem in '91 Cad. Fleetwood FWD, which is same as '91 Deville except for trim fender skirts. My mechanic said it was a broken window regulator. That part is not available new anymore, unless you can find some NOS. I bought a used regulator from Cadillacs Only for $75, and paid my mechanic for 1.5 hours of his time to r&r. Window now works fine. Not happy that I had this problem; regulator not a great design.

I have a 1991 Cadillac Fleetwood 4.9 120000 miles, I have the same problem. replaced plugs,wires,cleaned throttle body, and O2 sensor and have same problem. Taking it to a GM shop on 02/24/10.

try fuel pressure regulator

check the distributor cap and rotor, and plugs

i had the same problem and it died out of town got it towed and it was the fuel pump fuse and that was it they are famose for it

I'd take a look at the temp sender...the engines computer may be "thinking" the engine is still cold when it's not. That would cause it run rich (and rough) after it's warmed up. Generally the sender can be tested with an ordinary volt/ohmeter but you will need the specifications available in most inexpensive manuals. As with any complicated electronics system, I can only give you my best guess, without the luxury of doing any hands-on testing myself.
Good Luck!!

Reverse clutches are burnt. Clutch material is getting into valve body causing late shifts since valves can't move. transmisison will have to be overhauled. wish i had better news. sorry

the idiots must have towed the the car by the wrong end , this will burn out the transmission in short order. Any car needs to be towed with the drive wheels off the ground, if that is not poss then the drive-shaft has to be removed.

i am glad you asked
thats i the problem with the electronic select FWD system
when towing a FWD you should put both selectors in neutral this frees the transfer case and the drive shafts
how ever with the electronic system i dont know if it stays in neutral when the car is disconnected from the battery.
so you can make some tryles

1. put the car in neutral in both selectors "gear and FWD" while the car is running when all the warning bell and stuff have gone off turn off the car
   
2. now see if the car can be pushed or towed while the battery is connected
   
3. now disconnect the battery and follow step 2
   
4. if this works then all is well
   

i know when towing a FWD car u do need to put the transfer case in neutral to prevent damage
if you have the owners manual check under towing
if you don't, contact your local dealer and see what they say
hope this helps
ricko