My 86 NA 240 has been having trouble with a high idle. I cleaned the throttle body, flame trap and replaced the IAC. Everything seemed to be running fine, so I adjusted the idle per Bentley instructions grounding the connector to disable the IAC function and everything went well and the car ran correctly for about a month. My daughter (the driver) nows tell me the idle when steady is at 1100 and somtimes after starting it idles very rough. Raising rpms smoothes out the rough idle and the car will settle down to run fine except the high idle. I went out today and grounded the conection as I did to set the idle and it barely ran @ 450 rpms before dying. Restarted and it settled at 600 rpm and fairly smooth( I had set last month at 750). What direction should I take. I have been looking for a vacuum leak with a hose to my ear but have found nothing.

One note, the engine harness is the original biodegradable one with all wires to the firewal connector replaced. I have a replacement but have not taken the time to install. Should I go ahead and install it and then see if some electrical problem is at the root of all this?

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Dirk Story