so about 4 months ago i replace my sparkplugs and wires the cap and rotor still looked fine so i didnt change it and didnt have any problems with the car. the past 3 weeks its been cold at night and starting my car in the morning has been hell. and recently as your drivin at a steady speed and rpm the car is jerky kinda like the feeling someone is tugging on your shirt as your walking. i whent out and brought a new msd cap and rotor and K&n filter. i pulled all the wires off and notice the number 5 point the on the cap was dark and greenish and all 8 of the plugs were loose less than hand tight. i retighted all the plugs and put the new msd cap and rotor on, two days later it was still driving the same and the number 5 point was burnt up again.i checked the timeing and the flag has no marks but with the brownwire by the ac is pluged in the blancer mark isnt on the timeing flag but with it not pluged in its at the passendger side end of the big "V" its a 91 305 tbi any one know what can cause the car to burn up the cap like that or jerky when driving??

misfire on 5 I'd start with.
got a spark tester?

Make sure the #5 spark plug wire is fully seated on/in the cap terminal.

Timing is set with the wire brown wire unplugged. You're description of where the mark on the balancer is with the wire plugged and unplugged sounds normal.

The mark on the passenger side of the big "V" denotes that the timing is advanced. In general, this is where it should be. With the engine stopped, take a bright light and you should be able to see the graduations on the timing tab. Set the timing according to the sticker on the radiator support.

The bottom of the "V" is zero degrees or TDC.