Don,

I second Larry's experience that the idle speed on our XJ40s was typically 650 rpm and when put into gear idle speed would briefly sag then rise again.

Have you removed your IACV stepper motor and cleaned its pintle and the port in the valve body? If not, you may find that they are clogged with carbon that reduces airflow and idle speed. Before removing the stepper motor, be sure the key is out and then disconnect its electrical connector. If the motor is powered while removed from the valve body, the pintle can screw all the way out. I have photos in my albums at the link in my signature but I think only the thumbnails and descriptions may currently be available.

Cheers,

Don

 

This is true. Your photo albums are on the old Jag-lovers web site and all of the photo links there are broken so none of the photos actually appear when I click on them.
As you said only the thumbnails and the descriptions are accessible. That site upgrade they did over there really screwed things up and broke a lot of stuff.