I have a 1988 240 dl that idles at 900 - 950 rpms. I was attempted to bring the idle down to 750 with idle adjustment screw but had no success.

A mech told me he could bring the rpms down, then later said because my volvo was an old car you can't bring the rpms down. Is this true? I believe the spec says the car is supposed to idle at 750-850.

 

there is a screw on the throttle body you can use to adjust the RPM.

 

Are you sure the high idle isn't the symptom of a problem? A vacuum leak or bad/stuck idle control motor could be the cause.

 

As I mentioned earlier, I did use that idle screw and wasn't able to get it down below 900 - 950. Yes there could be other problems I suppose.

I'm just wondering if the mechs were feeding me a line of bull about 'you can't adjust the idle of old volvos'. Is the spec rpm of a 1988 240 dl 750 rpm, and can old cars keep to spec?

I'm a little pissed about the mech because they said turned down the idle, and the smog station said the idle wasn't changed at all.

 

Ohh I must have misread. If it was vacuum leak the car would surge up and down in RPM. If it were a stuck your car would die. You can try and clean your throttle body up a little, could be something holding your butterfly open or it is not sealing well.

 

The throttle body is that piece that the idle screw goes into, correct? Bolted under the carburetor? I'd better get a gasket for it if I take it off I think.

I guess I might have to start getting my fingers oily again if I'm going to hold onto this old car. I hope I can find a manual.

 

There is a two pin blue connector by the coil. You connect the blue/white wire to ground which should close the idle air control (IAC) valve. You then use the black thumb screw to adjust the base idle to 725 RPM. When you remove the ground connection the idle should increase to 750 RPM.

If it doesn't that would suggest a vacuum leak (split hose, etc) somewhere between the throttle plate and the intake, a problem with the IAC, the plate isn't closing all the way, or an issue with the throttle position switch (linkage) ... what has been said already.