I love novels especially "Who dunnits" or in this case what's causing it. :D
A lot of newer vehicles run mainly off the battery with the alternator just there for charging purposes. A weak battery can cause running dificulties all by itself.
Did you clean the EGR valve and port?
Check for any other vacuum leaks along the hoses and throttle body.
Clean the throttle body and IAC valve and port.
Check the IAC valve. It controls the idle.
Try tapping the throttle position sensor with the handle of a screwdriver wiht the engine at idle. Sometimes if they are going bad tapping on them will show up as asurge or stumble in the idle.
Try swapping plug wires and or coils and see of the miss moves also.
Check the fuel pressure at the rail.
Do a compression test to check for mechanical faults such as a broken valve spring.
Good hunting and let us know. :)
Tuesday, May 9th, 2006 AT 8:36 PM