: 1600x1067 px
: July 4, 2018
The test procedure is quite simple. Set the meter to read DC volts, and set the correct range if needed. Some meters will select the correct range automatically. Nearly all meters will come with instructions on how to set them to read DC volts. Next, connect the meter across the vehicle battery, positive (+) to positive (+) and negative (-) to negative (-). With the engine running at a moderate idle - say 1200 to 1500 RPM, the meter should read approximately 13.8 to 14.8 volts and be steady. If the reading is substantially outside these figures and all other items mentioned have been tested and verified good, then the alternator is likely defective.
An old oxygen sensor (say, 90,000 miles or more) may still work well enough that it doesn’t trigger the check engine light but could still hurt fuel economy. Engine performance can also be reduced by more serious internal problems, such as valves that don’t seat properly or worn piston rings, or by restrictions in the exhaust system. Because the same symptoms can suggest different problems, and there are often several possible causes and cures, it’s better to consult a professional mechanic than to try to be one if you have neither the experience nor the right equipment to diagnose drivability problems. In short, rather than ask for a tune-up, tell a mechanic what you’re experiencing and ask him or her to find the cause.