My 1998 cabrio only starts on occasion, and will suddenly turn off/stall when accerating from a stop if the engine is not warmed to it's usual driving temp. I already replaced the ignition switch, the spark plugs, and the cap below the spark plugs. Do you think it could be a relay problem? Like, maybe a #3 relay? please help.

clean throttle body,could be crankshaft sensor.

don't switched on the A/C suddenly after starting the engine take severe time for the warm up of the engine or u may go for full A/C servicing which include cooling coil,radiator cleaning

This canbe due to a faulty fuel pump or a failure of the HT circuit when the engine warms up or the circuit warms up.
The fuel pressure can drop when the temperature goes up in the engine so check the fule pressure when the engine stalls.
Secondly check the HT int he spark plugs when the engine stalls to confirm if there is loss of LT or failure of the HT coil or HT wires.

OK do the usual, check your plugs and check your plug sockets and leads for signs of shorting out against the cylinder head etc check the cap and distributor. My guess is that at least one of your coils (on plugs) has failed and this will reveal itself by the state of the spark plug(s) associated with it (them). Sudden stall when coming to halt with a hot engine and then to have immediate start up is almost always due to faulty coils(s). Strangely the propensity to stall is often reduced when the engine is still cold!!

I had a similar problem with a Ford Excursion, it turned out to be intake manifold gaskets. It would stall then start right up again, it ran fine during warm up. But, once fully warmed up it would stall at stop lights and stuff like that. I did get a check engine light, the code was lean condition. I don't know on a Jeep, sorry I can't be of more help.

I had a simular problem with my car nto starting, but the alarm didn't have issues just the headlights and the radio not turning off. I replaced the ignition switch and the problem was fixed for a while until the ignition switch malfunctioned again. The ignition switch is a cheap plastic part that connects the key to the engine, and has a tendency to break. Maybe this will help. Btw, I have a 1998 and mine is not starting well, do you know anything about #3 relays? I think I may need to replace it, so that my car will start and not putter to a stop randomly while driving. The problem only arises when the car is not yet warm. Amy ideas?

Is it an engine with a carburetor? If so, I can help with this information:

If the car stalls when it warms up, as you said, then here's a handy diagnostic article that specifically addresses this issue of yours, explaining the most probable cause of it:
http://yourhandymanzone.com/Your_Handyman_Zone_How_To_Pages_Vehicle_Car_Zone_Cars_Trucks_Vans_Engine_System_Engine_Stalls_When_Hot.htm

If the car stalls when you brake/stop, as you said, then here's a handy diagnostic article that specifically addresses this issue of yours, explaining the probable cause of it:
http://yourhandymanzone.com/Your_Handyman_Zone_How_To_Pages_Vehicle_Car_Zone_Cars_Trucks_Vans_Engine_System_Engine_With_Carburetor_Stalls_When_Braking.htm

These articles should help.
Good luck!
Brad

Have the crankshaft sensor replaced. This is a very common problem on this engine and it's a job best done at a shop because you need a special puller to get the crankshaft pulley off.

check your timeing belt frist . then check your fuel pump.and check your fuelter then check your fuese. 9 time out of 10 when a car die on you while driving its your timeing belt

Possibly faulty ignition module is the problem, stalls when engine is hot when you sit for a while it cools off and runs again until it heats up again, those are usually the symptoms of a bad ignition module and after a while it may give out all together and not run at all, usually if the module is at fault it shuts down the fuel pump so the engine don't load up with fuel, do to when engine continuously cranks over the injectors never stop squirting fuel and flood the engine do to lack of spark which is produced by the module, this could possibly be your problem.