What could be the reason for the number 4 spark plug to misfire on a Pontiac Grand Am?

Answer 1

if only the 4th, and all the time. the order for checking, is bad plug, bad plug wire. bad ground on that line, check the plug wire to make sure it is not cracked or melted and grounding out. If it is a 96 or newer vehicle, it has an obd2 data plug usually on the driver side under the dash. most chain parts stores have the tester and will run it, in the hope that you will buy the part necessary to fix it. If older than 96 then it is an obd1 and it is usually located under the hood and is best handled by a mechanic unless you have the tester necessary. also check the distributor for dirty contacts on the inside of the cap. clean all the connections on both end of the wires, it is a good idea to use a product called di-electric grease at the contact point of each wire. only do it one wire at a time. i can be confusing to try and remember which wire goes where if you pull all of them at once. hope it helps. duboff