Guest XR1000 Posted November 26, 2003 Share Posted November 26, 2003 I have a straight 6 runs like a top [1975 280Z ] however on start it will idle at 2200 after 8/10 miles will level off at 1000. I have no other complaints with the prime mover is this a adjustment or a problem. the prime mover is fuel injected. if this is a newby question then let me have it as a GT6-MK3 owner i have very thick skin! THANKS Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted December 11, 2003 Share Posted December 11, 2003 My 78 280z Service Manual claims a high idle results from a: 1) Dragging Accelerator Linkage 2) Defective BCDD system 3) Malfunctioning Air Regulator STRAIGHT FROM MY SERVICE MANUAL, "Quote/Unquote" The BCDD system stands for Boost Controlled Deceleration Device. Its purpose is to reduce HC emissions emitted during coasting. The BCDD, installed under the throttle chamber as a part of it, supplies addt'l air to the intake manifold during coasting to maintain vacuum at the proper operating pressure. There are two diaphragms in the device unit. Diaphragm I detects the manifold vacuum and makes the Vacuum Control Valve open when the vacuum exceeds the operating pressure. Diaphragm II operates the Air Control Valve according to the vacuum transmitted throught the Vacuum Air Control Valve. The Air Control Valve regulates the amount of addt'l air so that the manifold vacuum can be kept at the porper operating pressure. On California models, the operating pressure changes depending on altitude; thus, diaphragm II and control valve operations are adjusted automatically in coincedence with the altitude at which the vehicle is being driven. On Manual Trannys models this system consists of a BCDD, Vacuum Control Solenoid Valve, Speed Detecting Switch, and Ampliphier. On Auto Trannys models this system consists of a BCDD, Vacuum Control Solenoid Valve, and the Inhibitor Switch and Inhibitor Relay. The BCDD can not be disassembled and rebuilt-if it is defective it must be rpl as an assembly. If you dont have the BIG/THICK 1985 280z Service Manual you really need to purchase one; as it will advice you on how to test the components which effects the BCDD system. Hope this helps. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
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