[Razorback1980]

To test my injectors, I pull the fuel rail and put clear hoses on them and turn the car over and watch the spray. If it shoots a stream, it needs to be serviced. A friend of mine says to put a screwdriver on them and touch it to your ear and you can hear if they are working correctly...I haven't tried that method, but it sure seems easier than the way I do it. As for the cap and rotor, I only do visual inspections on them and other than that I change them on a routine basis like the timing belt. If you have excess grooves on the tips in the cap or the rotor looks really black and pitted on the end, I replace them. I do the plugs at intervals as well, however, you can pull them and look at their overall condition. If the tips are worn down, just replace them as they are so cheap that it doesn't take long to get your money back with the cost of gasoline. I check plug wires with an ohm meter or open the hood at night to see what their overall condition is like. If you see sparks flying around under your hood, they need replaced. The ohm meter works ok, but it won't always catch a wire that is sparking because you may have moved the plug wire away from the metal it is sparking against when you pulled it to check it. There may be better ways but I think that regular maintenance like we do timing belts is the best policy.