Strange Idle Problem

[CapoDiCapi87]

Hey everyone i have an 03 Sport and its doing something very strange. When I am idling and the air conditioning is off, it idles relatively well, a little shudder every 10 seconds but nothing major and its stays at about 500-600 rpm. But when the air conditioning is on its a complete different story. After i hear the relay pop, the rpm shoots up to about 800 and then slowly falls to about 700 and than rapidly falls to about 450-500 rpm and makes a weird clunk sound, about 3 clunks total as if the car was going to die. Than it stays at about 500-600 for a couple seconds, relay pops and the whole thing starts over again. Does anyone have any idea as to what this can be????? I have about 80,000 miles on the truck.

 

[IAmTodd]

Probably the IAC valve. Are you still under warranty?

 

[MONMIX]

Maybe the AC compressor has a case of the funk

 

[CapoDiCapi87]

Warranty

THanks for the replies, no im not under warranty, and also would I notice a difference in the A/C? i havent noticed any it seems to run strong and cold.