What makes a 1998 cadillac deville lope when started and won't accelerate when gas pedal is depressed

When you say it skips, should I presume you mean the engine lopes.? more information would help... Perhaps it sounds like it is doing this at idle, or when stopped in gear foot on brake or while driving.... It could be as simple as you having a loose spark plug wire, so lets start there, go push each wire onto their connection at both ends and check back and let us know more of whats happening, or if that fixed it

try replace throttle position sensor

Clutch plate and pressure plate seem to be too weak to pull the car. To test the clutch plate, park the car on flat surface. Pull the hand brake up, start the car, depress the foot brake pedal, depress the clutch pedal, put the car in 1st gear, press the gas pedal and leave the clutch pedal at once, while keeping the brake pedal depressed.
Follow one of the two following statements:
1. Engine does not shut down and remain start. (Clutch plate, pressure plate and clutch bearing defective - Replace all as a set)
2. Engine shuts down. (Clutch system is OK and does not require any repair).

idle air control is looking for base idle. throttle body base idle plate is dirty with carbon. cleaned out throttle plate with carb cleaner and tooth brush. use rags to catch black carbon.open plate.by some one hold throttle plate open with gas pedal. engine not running. after completed, start engine. run 1500 prm for a short time to clean out excess fluid. that should fix your problem..

try pluging egr vacume hose fixed my problem also loped when going down road at steady speed. hope this helps

Check the fuel pressure it souds like you might have a weak fuel pump.The fuel pressure should be 60-66 with key on engine off.

either turn ignition on and off four times or turn key on and depress gas pedal all the way to floor 4 times, 1 -2-3-4

WEAK FUEL PUMP OR STOP UP FUEL FILTER.RESTRICTED EXHAUST LIKE STOPPED UP MUFFLER OR CATALYTIC CONVERTER.LOW ENGINE COMPRESSION.VACUUM LEAKS IN THE INTAKE MANIFOLD.BAD PLUGS.WEAK SPARK OR IGNITION .

This usually happens when the fuel pump is loosing pressure.

I will just advice you make a replacement on the fuel pump. It is located in the fuel tank beneath the back seat.

Be sure to consider the rating on the fuel pump when replacing.

Good luck and rate my solution.

do u have a OBD 1 scan tool? try and find one on ebay for your car, I sold mine some time back, was $400 new got $50 for it, but I fixed allot of problems like yours because it allowed me to look at real time engine data going to and out of the engine control computer (ECM)