1990 Grand Am idle adjust

[AdamSean]

I just picked me up a 1990 Grand Am LE 5-speed. It runs good and idles fine with the AC off. But when I stop at a light with the AC on, the idle RPMs drop and is very rough. If I lightly press the gas while in neutral and increase the RPMs, the vibration stops. It seems the AC is bogging down the idle and so I was thinking of increasing the idle RPMs a little, but I can't see where to do this. On all my previous cars, there was a nut close to the throttle body to adjust the cable tension and increase idle speed. I don't see this on my Grand Am. Does anyone know how to change my idle speed. Thanks guys and gals.

 

[melsg5]

the engine has a IAC, idle air control, valve. It may have carbon build up or need replacing or has a wire harness issue. In addition check the throttle body for carbon build up.

 

[AdamSean]

Thanks. I will check that. My old Saturn also had an IAC Valve, but also had the cable adjustment. I just thought that was weird. The throttle body and IAC Valve are under the air filter housing, right?