Single cylinder misfire? I'd be thinking failed/failing HT lead to the spark plug, failed/failing distributor terminal (if present,) failed/failing fuel injector (which could present as a single cylinder misfire,) or something else that would affect that cylinder only in an electrical sense.
First step of troubleshooting is to confirm the diagnosis - if the OBD is reporting a #5 cylinder misfire, idle the engine and either pull the spark plug (HT) wire or the fuel injector wire on #5 and see if the idle changes. If it does, OBD is wrong. If it doesn not, you can start to work on figuring out why.
OK - it's a 1998, so it should still have a distributor. Make sure the cap terminal for the #5 cylinder is not loose - it's been known to happen. Also, make sure to use a cap with brass terminals vice aluminum - the aluminum terminals tend to corrode and erode rather more than the brass do (aluminum is the silvery colour, while brass is like copper, only with a bit more yellow. I've found that BorgWarner caps tend to consistently have brass terminals.)
If you have an OBD-II code reader, flush the codes and see if it comes up again. If you do not, get one - they can often be had for less than $100.
I have a 98 jeep cherokee 4.0 and since ive had it sounds like there is a miss had a anilizer on it said 5 misfires and 6 is staying open cleaned injecters new spark plugs wires cap and rotor new brain and fuel reg fuse got a p1282 code but still runs the same and vibrates once it reaches 45 and will go away when you hit gas but returns when you level off change injecters around and still sounds like miss on 5 if you try to ground it out to see which one is giving issues boggs down on 12346 but 5 acelerates but still missing check engine light came back on again but only shows p1282 help dont know what else to do family has to drive arond in it and dont want another broken vechicle last one blew up
i have a 98 jeep cherokee 4.0 and since ive had it sounds like theres a miss had a anilizer on it said 5 misfire 6 staying open put new wires,rotor,cap,sparkplugs, took fuel injectors out cleaned put back in different order also hooked up new brain gave a p1282 code but other things sounds like a miss tried killing 5 and it revez higher no change in sound when i kill 6 off when going over 45 bad vibration hit gas goes away until speed levels off vibrates again at any speed over 45 if i coast no vibration until touch the gas please help my other vechicle blew up and my family has to drive this one any answer would be great seen alot of simular post but havent seen the right one yet
