Jim Grant's Tech Tips
‘96 Chevy Caprice, Idle Speed Problems
Q: Can idle speed be adjusted on my ‘96 Chevy Caprice with a 6 cylinder? Frequently at idle, the power steering assist is poor and the Low Battery Voltage light comes on. When engine speed is increased with the accelerator pedal, both problems are corrected. I understand idle speed is controlled by a computer and may not be adjustable. I would very much appreciate comments.
- Dick Galer
A: I don’t think there is a vehicle made today that doesn’t have a computer controlled idle speed. With that said, you should know that there is what is called a base idle speed setting. Tech’s often refer to base idle speed as minimum idle air settings. The procedure for setting minimum idle air varies from vehicle to vehicle manufacturer. However, the procedure in most cases calls for adjusting the position of the throttle plates with what most people would call an idle screw. But, there is a word of caution. The minimum idle air setting is a baseline for the computer to operate from. If the computer is not turning the idle speed up as you think it should be there may be a different problem. The control of air speed above the minimum setting is the result of the computer actuating an idle air control motor. I would suggest having a scan tool plugged into your vehicle’s computer and have your technician check (in GM vehicles) the idle air count. The idle air count is the computer reporting what position the idle air control motor is being commanded to open. With this information the tech can then determine if there is a problem with the operation of the idle air control motor, or if other service is needed. Word of warning, if you just go in and turn what is perceived as the idle speed screw you can really alter the computer’s response, creating a variety of driveabilty problems.