IAC Question, outta the norm
02-19-2007, 11:06 PM
#1
4th Gear Member
Thread Starter
Join Date: Jan 2006
Location:
Posts: 1,143
IAC Question, outta the norm
Does your Idle Air Control Valve stay open at all times? Just curious. If it is, that would mean its unmonitorered air calculated into the A/F mixture right? Mainly asking all this because of the IAC Restrictor plate to reduce hanging rpms, wouldn't it make you run a little rich?
02-20-2007, 06:11 AM
#2
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
RE: IAC Question, outta the norm
The IAC valve only opens when the PCM tells it to, the computer can also control how much it opens by varying the duty cycle of the control signal.It opensat idle with the AC running (or some other load such as the alternator, p/s etc.), and when you close the throttle at higher revs and the engine is decelerating. [/align][/align]On my '03 GT it's also open until the car actually stops rolling (I've thought this might have something to do with the hydro-boost brakes, keeping the idle high keeps the p/s fluid pressure higher).[/align][/align]One last thing, the air passed by the IAC valve is metered, it's taken from the intake hose after the MAF. A restrictor just limits the rate at which the air can flow and makes the IAC valve perform "sluggishly" so the revs drop faster with the throttle closed.[/align][/align]
02-20-2007, 08:47 AM
#3
5th Gear Member
Join Date: Nov 2006
Location: Bay Minette Alabama
Posts: 3,080
RE: IAC Question, outta the norm
ORIGINAL: cliffyk
The IAC valve only opens when the PCM tells it to, the computer can also control how much it opens by varying the duty cycle of the control signal.It opensat idle with the AC running (or some other load such as the alternator, p/s etc.), and when you close the throttle at higher revs and the engine is decelerating. [/align][/align]On my '03 GT it's also open until the car actually stops rolling (I've thought this might have something to do with the hydro-boost brakes, keeping the idle high keeps the p/s fluid pressure higher).[/align][/align]One last thing, the air passed by the IAC valve is metered, it's taken from the intake hose after the MAF. A restrictor just limits the rate at which the air can flow and makes the IAC valve perform "sluggishly" so the revs drop faster with the throttle closed.[/align][/align]
The IAC valve only opens when the PCM tells it to, the computer can also control how much it opens by varying the duty cycle of the control signal.It opensat idle with the AC running (or some other load such as the alternator, p/s etc.), and when you close the throttle at higher revs and the engine is decelerating. [/align][/align]On my '03 GT it's also open until the car actually stops rolling (I've thought this might have something to do with the hydro-boost brakes, keeping the idle high keeps the p/s fluid pressure higher).[/align][/align]One last thing, the air passed by the IAC valve is metered, it's taken from the intake hose after the MAF. A restrictor just limits the rate at which the air can flow and makes the IAC valve perform "sluggishly" so the revs drop faster with the throttle closed.[/align][/align]
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