got a 98 dodge ram 5.9 with engine light keeps comin on. code says #5 misfire. po305 seems to run good for the most part, feels a little under powered but runs smooth. sometime it pulses lightly when i first let off the brake but nothin major, doesnt really hesitate. i replaced the plug didnt help, i replaced the wire,nope. finally i replaced the #5 injector and still no change . not better or worse. any suggestions. really annoying havin that light on. i erased the code several times after each fix and still comes on. ???????? plz help thanks!!!!!!!!!!! also i made sure the wires arent crossed....hmmmmm

 

unplug the pre-cat O2 sensor and see if it makes any difference. 95% of the misfires are due to bad O2 sensor...

 

Check your wire routing. #5 and #7 can cause misfires if not routed properly.

 

I just had the same problem with my 2002, your distributor cap and rotor could be the culprits. It would be worth doing an inspection of these. With my #5 misfire i changed the plugs, wires cap and rotor and it solved the problem

 

buddys 98 had the same problem took the cap and rotor off, completely shot replaced them and the pre cat o2 sensor was bad so i replaced that, check engine light went right off and it ran perfect

 

misfire on a single cylinder won't have anything to do with O2.
check/replace cap and rotor, maybe replace wire #5, or at least swap it with another cylinder.

next step is to check compression to check for major malfunction.

 

its more then likely the cap and rotor, bet when you take yours off and look inside itll be filthy

 

You may also want to check the el. plug to the injector on #5. Once I had a misfire and it turned out that the plug was missing the little retaining clip and would come just a bit loose, but enough for a misfire.

 

This one time, at band camp...

 

LOL VW i don't wana know where you put your sparkplug lol