idle speed, higher or lower with aircon?

[vinnY]

been finding conflicting reports, just wanted a definite answer

is the idle speed supposed to increase or decrease when you have the a/c on?

i figured the iacv should compensate and if anything the idle should be a bit higher but oddly enough on my car the idle with a/c seems to drop about 2-300rpm from the normal no-load idle

anyone want to confirm what's right and wrong?

[2MPRS]

mine drops down aswell when i have aircon on

[cazz'shonda]

Will say that the norm' for modern cars with comp controlled idle etc is for the idle to be increased when the a/c cuts in. It can drop back a little when it settles but it's not usually the case as the engine could stall at the lower rev's due to excess drain of the a/c comp. My Renault picks up revs when the a/c is turned on or cuts in. Daughter in law's Jazz does so to.
Maybe your IACV is dirty? Give it a spray out with some carbie cleaner.
If the car has an EU with set idle speed, it should at least return to it's set idle. Only auto's in my experience have different idle limits for park and dirve/in gear.

{ A bit of history, even cars back to the Ford XE/XF Falcons had a/c compensation circuits in the carbies, operated by vacuum valves. The a/c would cut in, vacuum would drop due to lower revs, the valve then opened increasing the revs. }

[DC2-PWR]

You also lose power and get worser fuel consumption with the a/c. But I love the a/c :D

[Bludger]

I believe the engine tries to compensate for the extra load.

depending on condition of the engine & various factors, the idle speed could either be higher or lower.

just depends

[Limbo]

car does increase idle, but the a/c pulls is back down due to the compressor sapping the power.
that's why u get the 2-300 lower

[vinnY]

isn't the iacv supposed to make the idle settle?
i.e. normal idle is at 1k, with aircon it'll bump down to ~700
shouldn't the iacv bring it back up to 1k?

gonna check my timing tonight then reset my base idle see if it does anything

[ECU-MAN]

yes the iacv is ment to up the rpm to compensate for the drop on pgmfi
on dual carb it uses the eacv and idle up mech

[vinnY]

ah okay, does the iacv work relative to the base idle or does it have it's own set parameters?

i.e. the stock idle rpm for my motor is 800rpm, i've got my base idle set to 1000rpm
if the iacv raises the idle 200rpm, will it raise it from my base idle or the pre-programmed idle from factory?

[ECU-MAN]

the IACV will raise the idle to a pre programed value, so if your base idle is out then it wont be able to coreclty compensate

[vinnY]

ah fair enough

thought it'd be smart enough to go relative instead of absolute

such as in my situation i have a chipped ecu and need to idle at 1000rpm instead of 800rpm because of the larger cams
revs seem to drop too low and the car shudders which i'm guessing is because it's trying to get the iacv to idle at 800rpm instead of the higher figure