[MudderChuck]

What year XJ? You can spray some oil into the IAC orifice while the motor is running. This usually loosens them back up. If it's a Renix (Pre 91) remove the IAC and clean the pintle and seat, let a few drops of oil run behind the pintle (piston). They get pretty gummed up. After 90 they usually just need a few squirts of spray oil. I avoid heavy use of solvents on the IAC, because the pintle rod is lubed from the manufacturer and solvents may wash the grease out.
Don't try to move the pintle (piston) by hand, this can damage the rod and tiny drive gears.

There are other reasons for the motor to die after a few seconds. Depending on the year the list of probabilities changes some.