When should spark plugs be changed?
My car has 100,000 miles and runs better than when I bought it. It has the original spark plugs. A Toyota RAV4 owner’s manual says to replace the spark plugs at 120,000 miles. If I were you I’d replace them when they fail resulting in an engine ignition misfire. However, on your GM engine, it’s possible an engine ignition misfire can damage your ignition module and coil. So I would first remove the spark plug connections one by one and clean them to make sure there’s no corrosion in the plug wire connectors or the coil pack contacts. http://www.aa1car.com/library/misfire.
If you change the plugs you are just guessing what the problem would be. You can do what you want but if you change the plugs, filter, air filter, plug wires and anything else you can think of and it still runs bad you just wasted 300 dollars for nothing. Take it to a mechanic and spend 100 to find the real problem.
