I recently bought a 2001 Jeep Cherokee Sport with 184k miles on it. It runs good, but the check engine light is on. I hooked up a cheap OBD-II scanner I got on Amazon and it says the cylinders are misfiring. I then took out the spark plugs and they're in terrible shape. I went ahead and looked around on this forum and everyone seems to recommend either the Champion Copper Truck Plugs or the NGK V-Power ZFR5N plugs. I went ahead and bought some NGK plugs. I am going to install these today and see how it goes. The old plugs gave the Jeep a rough start and rouge idle, and it seemed to suck down more gas than it should. Besides spark plugs, what are some other things I should look at that I could do maintenance wise? At 184k miles, I am sure something needs cleaning or replacing.