Okay, don't shoot me, if you have heard me on this subject ten times before, but I am continue to be mystified by the fact that my 745 Turbo (1991) idles at between 550 and 650 when fully warmed up (that is what the onboard tach says, on the dash board). I have done all of the obvious things, believe me - IAC, checked AMM, new TPS, adjusted it precisely, throttle body cleaned to within a millimeter of its life, RPM sensor, fuel pressure sensor, ECT sensor, and a few I haven't mentioned. None of the obvious things have affected the idel AT ALL. I even found a used ECU from a guy on ebay to see if that might be the problem and it made not a hint of difference (both ECU's are probably fine). Broke down and went to Keeler Volvo here in Albany to see if they could diagnose it and they didn't even pay attention to it as a problem, so maybe I need to just forget about it and get a life!

Thanks for listening and for your patience with my struggle with the low idle problem. I even had someone bring this up at the local VCOA chapter meeting to see if anyone had any insight, and nada! Any ideas???
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Darius in Albany NY '86 744 GLE (175K, given to my mother-in-law); '91 745 Turbo (167K-my 'Little Red Wagon')

The LH 2.4 systems idle different than the other systems. The base idle still needs to be set but I think your idle is good where it is. To check to see if it needs adjustment crimp the hose that runs to the manifold from the CIS motor. Do this slowly, and the car should continue to idle and not stall. if the car stalls clean the throttle housing out and make sure it is very clean. the car should idle around 500 with this hose closed. If the idle is lower but the car still runs then I woudln't worry about your idle. FYI the 2.4 system don't ahve a fast idle like the others. When the car is cold there is not much fast idle on LH2.4 the system lengthens the injecter pulse to enrich the mixture.

Steve - This helps, and I thank you. When cold, the car idles low compared to my 1986 740 (LH 2.2??) and I had a feeling there was some adjustment that was being made to make this possible. Same with the a/c - the idle doesn't increase with the a/c, but I am sure some compensation is made as it works just fine. I guess I will stop worrying about it.
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Darius in Albany NY '86 744 GLE (175K, given to my mother-in-law); '91 745 Turbo (167K-my 'Little Red Wagon')

You should clean out the throttl ebody as dirt build up can give you a fault code. It also will affect the idle. Make sure it is clean and I would check the base by clamping the hose to make sure and yes your other car was probably LH2.2.