J H

What is the expected idle speed for the 1985 corvette. When idling with the AC on, my alternator light comes on. I am believing that the idle speed is set too low. Any ideas??????

vader86

idle should be at about 600-700rpm

rons85

But... (there is always a But)... The computer is supposed to maintain the correct Idle speed using the IAC (Idle Air Control) motor. There IS a "manual" idle stop adjustment (which was sealed at the factory, but has most likely long since been uncovered by Someone...), so you could "turn it up" yourself - at least the minimum speed, but if you set it up to where you want it in gear/AC on then it will probably be idling too high the rest of the time. Better to figure out why the computer isn't controlling it correctly - bad IAC, dirty Throttle body (common problem), etc.


[Modified by rons85, 8:08 PM 7/7/2004]

vettenut85

base idle speed for a 85 was 450rpm,later gm reccomended base idle speed reset to 550rpm.i have reset mine to 600-700 as vader has said.


[Modified by vettenut85, 6:47 AM 7/8/2004]

darkman5001

You have to set the base idle by first grounding out your diagnostic connector (ALDL), turn key on but DO NOT start. Wait 30 seconds, then while the key is on, unplug the connector to the IAC. Then start it, and allow it to go into closed loop. You may have to keep your foot on the gas a little to keep it runnign at first. When it goes into closed loop, your engine light will go from blinking slower to a fast blink. Once you are in closed loop, set idle speed to 450rpm. You may need a more accurate portable hand tach to get a accurate reading. Once you set it at 450rpm, shut down the engine. Reconnect IAC, and unground the diagnostic connector (ALDL.) Next set TPS sensor. You must check and adjust if needed after settign base idle, as the computer sees both of these things for setting idle speed. Let me know if you need more info. I have ALLDATA, and a Corvette manual. Good luck...