Hey my ranger is acting up, the rpms move up and down when it idles but when im driving its perfectly fine. It has a little vibration to it. It may have a little loss of power but thats it. I checked the coolant to see if theres a head gasket leak, but no coolant loss. It had an engine light but i reset the computer and now it doesnt come on. I did a code reader and no codes came back. It just happened when i changed the spark plugs and wires because my radiator cracked and it overheated so the spark plugs were glazed. So i changed them and now its acting weird. I looked at the idle control valve and i cleaned it out. it still runs strange. I also heard to unplug it when its running to see if it changes and mine just dies. I checked the coil pack and its sending spark to all cylinders. I havent changed the fuel filter. The truck has over 70,000 miles on it. What do you guys think i should do next.