misfire/knock problem

[6shooter]

I have a 99 3.8L auto and am experiencing a little problem. I'm throwing a code for cylinder 5 misfire even after checking coil pack and replacing the plug. The weird thing is that it only misfires in 3rd gear (maybe 2nd I'm not sure) when the RPM's get 4500-5500 and speed tops off about 65/70. The car stops revving any higher and won't shift into a higher gear until you let off and accelerate slowly. If you hold the stuck gear to its max for like 2 seconds, it sounds like a golfball in the engine or like the fan or flywheel is hitting something (maybe knock retard) and then SES blinks Cyl. 5 misfire...I dunno if it might be a tranny problem too or if the not shifting and misfire are related. Anyone have similar issues or any suggestions. It would be much appreciated...I'm not into paying a couple hundred at the shop if I don't have to.

When my tank is empty I'm gonna try some 89 or 91 octane to see if it really is knocking (I always run 87). I need to get this figured out before I use the bottle for the first time. P.S. my car has 63000 miles.

[ribbed4hr2]

i hade the same sorta thing try replaceing the wire next if that dosent do it it might be somthing else.

[mcjoslyn]

How did you check the coil pack? You may want to swap it with another cylinder to see if the misfire changes cylinders too. It sounds like a breakdown somewhere that is being triggered by a high load. You should also try swapping the plug wire. How does the new spark plug look? Is it a light brown color?

[6shooter]

AutoZone guy said to check conductivity of the coil pack, pull the boot off the coil and see if a spark jumps across and it definately did. The sound my car is making is the same sound it made when the boot was held just above the coilpack so I think it's the plug wire or boot failing under high load and making the clicking noise and triggering a misfire, but I don't understand why that would prevent the car from shifting.

Thanks for helping, both of you guys.