jeep has spark but wont fire

i have 90 xj 4.0 that wont start. it died yesterday. it turns over and u can hear that it wants to start sometimes but it wont fire. what happend is it ran fine in the morning stopped to drop off the kids got back into the jeep and put it in reverse and it started to die. had to turn off the heater stereo just to make it to work. then got back in it and started it up put my foot on the brake it started to die put foot back on brake and put it into gear and it died. im stumped :helpme:

bad fuel filter or no gas is what it sounds like.

Make sure all your grounds are good, then check to see if your alt is putting voltage to the battery. And that the battery is sound. An auto parts store can run a test for ya. I am thinking this as you say you have to turn off stereo and heater for it to work, Otherwise its fuel. (not getting enough) Good Luck

Not firsthand advice, but two thinkgs that I've read about that come to mind. Try starting it while feathering your foot on the gas. If it's the IAC gone bad, you should be able to get it to start and run .. just won't idle. Also, you might try running without your ballast resistor, should be able to search for instructions on how to do that.