on a 2004 grand am i haven't change them ever since i pruchase the car in 2005.How do you know when its time to change your spark plugs or alternator?
With spark plugs, normally your gas mileage starts to decline and when taking off, it is getting sluggish. Or you can always check them, if the gap is big and they are black and corroded. Normally change them every 15,000 miles, but check them first. Your alternator, well since it keeps your battery powered (generator), all the things that are run by your battery (lights, radio, other electrical devices). Lights seem dim or your car will hard to crank over other things such as that.How do you know when its time to change your spark plugs or alternator?
When the alternator is about to go out, your AC, radio, gears with go on and off, car will go in and out of gear like it's dying then coming back to life.
Spark plugs? It's hard to say. But they're cheap to replace and improve MPG, so do it every few years.
