dude,

i had the same problem before with my compressor. i had everything checked from tps, tune-up, new throttle body pero d pa rin ang idle-up.
then ang lakas sa gas. and maingay compressor, especially when it engages.

what i did is that i removed the ground of the compressor then i started the engine turnd on the ac. the rpm shoot up to 2500; w/c means the idle up is working.

the culprit...compressor. althugh the ecu sends an idle up signal to the engine, hindi kaya ng engine coz hirap sha paikutin yung compressor. which in return gives heavier engine load and decrease in fuel efficiency.

after replacing the compressor, everythings was a s good as new. :D

just sharing my experience...