Swap the fuel injector with another cylinder's injector, then see if the temp difference changes to the other test cylinder.
Check the lobes on the intake and exhaust side of the cam shafts on that cylinder, make sure they haven't been ground down.
If this problem only happens on idle, pull the air bypass valve on the throttle body for that cylinder and make sure its not clogged.
Check for carbon buildup, use a camera from Lows (you can return it after using it). Perform a compression test and see if that cylinder is significantly different from the rest. A leak down test would also be useful if you have the equipment.
:: Just a shade tree mechanic keeping a 75,000 mile beast alive.
Last edited by antaren; 07-21-2012 at 12:31 PM.