alright guys and gals this happened on my previous xj did this but it wasnt as evident but anyway here it goes...when i turn on the a/c when im idling you can hear a surge. its like every 5-10 secs and the surge only last about a couple secs but you can actually see it a bit in the RPM but just wasnt sure if im pretty much waiting for something to go wrong

 

sounds like it's just your a/c pump engaging.
it should engage when either your hvac (a/c) settings or your defrost setting is selected. which actually uses up more fuel.
it shouldn't engage when either the floor or vent settings are selected.

it sounds normal.

 

mine does that too if you open your hood you can see your AC pump engage its totally normal

 

In addition, the Idle will increase when the A/C compressor kicks on, as the computer is programmed to bump the idle speed to compensate for the load of the compressor. This is completely normal.