Rough idling when aircon thermostat is on....

[mark_t]

you might have a malfunctioning idle-up system.
an idle-up increases the idling rpm of the engine when your aircon is on, because aircons eat up significant engine power. if they do not idle up, you would get a rough engine idling. namamatayan pa nga...
but why don't you have this rough idling when the engine is freshly started from cold? because your engine choke is still functioning. it functions like your idle-up, but only when the engine is cold. when the engine gets hot, this choke signs off. and that is when your problem starts..
... i think..
good luck.

oops... diesel pala. at isuzu pa.. ewan ko if if my explanation still holds..
iwan ko na lang dito, at baka may makinabang..

Yes, it still holds. Its idle control valve, local mechanics and stockman call it VCV
or vacuum control valve. Just follow that rubber hose the size of spaghetti for leaks.
Most of the time it just falls off for some reason so you have to put it back on.
Or replace for a new one.

You check it by covering the hose with your finger to feel if it sucks air.
If it sucks air then it works and simply put it back on.