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08-14-2001, 04:08 PM
Where does the signal come from for the idle control module to actuate the idle control valve. Let me rephrase the question - How does the idle control brain box know what the engine speed is? From what I understand, an '86 735i should idle around 800 rpm. Is the signal taken from the tach? Or is it taken from the flywheel sensors? Does the idle control valve have a engine temp sensor somewhere in the coolant circuit?<p>I ask because I believe my ICV is shot. It is the orginal part (15 years old). I took it off my car last night and checked the valve position because my engine has been idling at around 1000 hot and 700 cold. Do the idle brain boxes go on these cars? I am just preparing myself for the worst - the new ICV won't help the idle. If so, is there a sensor as the culprit?<p>Thanks,<p>Fife<br>

08-14-2001, 09:10 PM
Fife your car does not use an idle control box. The Motronic handles it for you. To be sure of this look at several things.....<p>1) Do you have a screw on the idle control valve?<br>2) Does your ICV have three wires?<br>If you answerd no to the first and yes to the second then you have no ICV box. Motronic uses all of the engine sensors to control cold start, Idle speed, etc. Check and see if ICV is staying open at all. Sometimes you can clean them with brake cleaner and they will start working. <p>Something I just learned from Jens(yea old BMW Guru of all times)that if you have a vacuum leak in your HVAC system this will also cause the idle system not to work right. You can test this by pluging off the line from the manifold to the HVAC pump. If it starts idleing right(no AFM opening at idle) then you found the problem. Also if none of the above works check to see if the idle control micro switch under the TPS is engaging if not this could be it. <p>These are just afew places to start hope this helps.<p>Jon<br>

Jens T.M.745
08-14-2001, 09:43 PM
Thank you Jon!<br>Its good to know people get resolves from some of my stuff,<p>Also 86 735 does not have an Idle control<br>screw, yet an Idle control box,<p>but I agree with all Jon said, first things first.<p>Sincerely Jens

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