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Have a slight idle surge or hunt of about 200-500 RPMs at hot idle. Hot Idle set at around 1000 RPMs. The idle smooths out when I disconnect the o2 sensor. The sensor is a brand new bosch one wire universal. The old one had been disconnected by PO and never noticed. I've done away with the Bosch AAV and installed a man op one, If that makes a difference. Also replaced hoses in the eng compartment. ??????? Thanks in advance for your help!

1983 Spider
 

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1966-2013
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The O2 sensor has little or nothing to do with the idle speed/mixture as the ECU reverts to open an loop mode when the TPS indicates the throttle is at idle.

Check the TPS for correct orientation and hope that the PO didn't tinker with the throttle stop screw on the throttle body at around the same point he disconnected the O2 sensor.


Click the link in my sig block for more information on the system.
 

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Below are the Items that I found were causing a surging idle during the course of owning my 87 spider:

1) small vacuum leak due to bad brake booster.
2) small vacuum leak due to bad vacuum sensor in rear shelf area (do you hear hissing/whistling?)
3) burned valve - possible but unlikely
4) also check hoses to oil separator particularly small vacuum hose and large hose from valve cover to oil sep.
 
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