I have a '96 fuel injected 460 that likes to idle around 900 rpm. The throttle bypass valve is a likely culprit, but the resistance checks out (10 ohms).
When I disconnect the lead to the bypass valve, the engine hangs out around 650 rpm. I have adjusted the butterfly's to almost closed, but the bypass kicks the rpm back up to 900.

I don't have an obd II reader, but it's not lighting check engine lamp.

The bypass is being told to kick up the rpm's, what other input would cause this....bad 02?

Not sure if the procedure is the same on an EEC-V 460 but here it is for the EEC-IV system.

http://users.superford.org/ylobronc/documents/idleadjust.html

The two things off the top of my head that affects idle rpm is the water temp sensor (raises rpms to cool down if it gets over a certain temp) or the A/C system (raises rpm to compensate for the a/c clutch kicking in).

Thanks for the link, I will check it out.

I have to rule out the temp sensor since it drops to 900 rpm from about 1200 when it goes into closed loop on from a cold start.

The a/c clutch isn't engaging when I am testing it, but the motor will compensate for it when the a/c is on.

I am wondering if an O2 sensor is falsely claiming a rich mixture so the ECU kicks up the air intake through the bypass valve. Or maybe the mass air flow sensor isn't detecting enough air flow, so it lets more in through the bypass valve.

Something is triggering the bypass valve to kick in during idle, I just need to figure out what....