I agree with Fordin K - except I don't think the '94 Jeep Grand Cherokee has a PCV valve. The air filter should also be replaced if it's been a while. There are "tune up kits" available online, which contain all of the above items (distributor cap, rotor, spark plug wires, spark plugs, fuel filter), or you can buy them individually at someplace like AutoZone or Advance Auto Parts. Just give them the make, Model, & year and they'll get you all the parts. With things like spark plugs and wires I just go with a "typical" brand, as I don't find value in the more expensive "super performance" models of these basic tune-up parts. The whole shopping spree should cost less than about $80.