I have no exact data of what the base idle rpm should be on a 24v. You'll have to do it by trial and error. But the procedure is done like this:-
Below is the procedure for a 3.0 V6 24v. I used to do this for a living and it isn't that hard if you're handy with a screw driver and willing to learn.
1. First you make sure that you have no air leaks in or around your inlet manifold, intake tubes, throttle body, brake servo, plenum chamber, injectors, airflow meter etc. You do this by warming the engine up fully then unplugging the ISCV (Idle Speed Control Valve) and then with the engine running (it will be idling faster than normal) spraying with a can of "cold start" or "start it" in the area of any possible leak sites. If the spraying causes the engine revs to increase or decrease you have found the site of a leak. If the engine revs stay the same while you are spraying then you do not have a leak. You may now put the plug on the ISCV back in.2. If you have a leak, fix it before doing anything else!3. If you have the facilities to do so, check the mixture using a gas analyser. If you do not have this facility then you can skip it, but if there is a problem with your mixture control it will effect your idle control. On an engine with a catalytic converter, if your CO% is 0-0.2% then you can move on to the next step. If the CO% is higher than 0.2 you have a problem. If so check the O2 sensor is switching. You should find that the signal wire shows the voltage fluctuating, up, then down, up again then down etc. (if not, replace it).You might think this is a hell of a rigmarole just to adjust the idle, but it should be pointed out that the idle speed should control itself, therefore if your idle is incorrect then you have a fault somewhere. or someone has already been fiddling with it and messed the settings up.4. Now unplug the throttle position sensor (TPS) on the side of the throttle body. Loosen the screws that hold the throttle position sensor so that it may pivot freely.5. Remove the black plastic cover that goes over the cable side of the throttle mechanism. You should now see a small throttle stop screw on the top of the throttle body. Squirt some WD40 or similar onto the screw to help make sure it will move freely (it may be tight due to never having been adjusted before).6. With the engine running, you may now set the idle speed using the throttle stop screw to approximately 975-1050rpm (make sure you use a GOOD screwdriver for this as it is very easy to mess the head of the screw up). You may find your 24v engine works better at a different setting so you will have to use trial and error here. PLEASE NOTE THAT THIS SETTING OF 975-1050RPM IS AN EDUCATED GUESS (I don't have the exact figures in any of my data files).7. Turn the engine off.8. With the engine still turned off but with the ignition on, set/twist the TPS so that in the throttle closed position the voltage from the signal wire is 0.5v. Tighten the screws holding the TPS in this position. Make sure that you haven't used too much force whilst twisting the TPS or you might find that the throttle doesn't return all the way to the throttle stop screw! Now recheck the same wire with the throttle fully open and make sure it is as close as possible to 4.4v.9. Make sure you haven't dislodged the throttle cable from the cam that it goes around (often happens when you're operating the throttle manually from under the bonnet). If you forget this step you may find that your engine will rev its balls off when you restart the engine!10. Restart the engine. Check the idle is still between 975 and 1050rpm or at the same setting as it was before you adjusted the TPS.11. You may now plug the TPS back in. The engine revs should now decrease to about 650-800rpm (if the revs are too hi or low start the whole procedure again and set the base idle at a different level).Thats it, you should by now have successfully reset your "base idle speed".If you still have problems, then you might suspect ISCV but it is probably best to call in a diagnostic specialist/engine tuner at this point. He would then test the ignition system, wiring and other things on an oscilloscope before replacing parts willy-nilly.
by: sportstron @ alfa 164 register http://www.alfaromeo164register.com/viewtopic.php?f=2&t=928&start=25
