# idle air control valve



## matt_101 (Feb 5, 2007)

1990 Nissan 240sx 
KA24E

okay...... so i have been having ideing problems for a long time. good gas, NGK R plugs, new cap and rotor button, new plug wires(and coil wire). 

Specifically the problem is after driving the car it takes a while to return to idle. i have tried adjusting the screw on the idle air control valve to tighten/loosen the spring, this does bring my idle up and down but it still does what i described before. i unplugged the lime green plug on the back of the unit and the car seems to be running perfect now - is there any harm to leaving this unplugged? from what i can see and from some of what i have read the idle air control valve only helps you start when the motor is cold. 

Here are all my mods:

Stage 3 clutch ( 6 puck center sprung)
11.5 pound flywheel (stock is 22.5)
injen cold air intake( the long one)
cat removed (replaced with test pipe)
generic fart can type muffler ( it was on the car when i bought it)

Thanks - hopefully i can finally put this idle issue to bed. lol


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## OchnofConcrete (Jan 7, 2008)

that is what it is for... it has a therma sensative material that senses when the engine is below operating temp (any time the car's off) and it basically makes the car idle a little higher because of this:::::......

when a car first turns over, there isn't enough pressure/ revolutions in the system to pump oil correctly. the worst conditions for a motor is a: start up b: oil starvation... when starting up, all the oil's at the bottom of the engine. so to get a correct amount of oil pressure for start up, the AACV, ACV, and I-ACV (all solenoids and valves that work together in the same little space) makes the car idle differently... higher. during other situations... like the knock sensor giving a code, or another sensor.. the idle operations play with the idle so the car is operating at PRIME CONDITION. most likely the reason why it's not idling correctly (like most of all old cars do) is because some sensor is telling the computer to send a code to the ICV's and change the amount of air given to the engine. 
the thing you have to keep in mind is that if you never fix the original problem, the ICV's will continue to play with your idle mixture.
what might help........
new vaccuum lines, full maintenence procedure, TAKING THE ICV'S OFF AND CLEANING THEM w/ CARB CLEANER. same thing that happens on a carb, happens in the intake and idle systems.

but just keep in mind, the ICV's are not active sensors, they are solenoids and valves that react to what the ECU tells it to do... via ANOTHER SENSOR.


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## rogoman (Dec 16, 2004)

Here's something else to check:
If your engine continues to idle real high after it's warmed up, check the air regulator unit. It's located on the passenger side of the engine, below the intake manifold, near the rear. There's a hose connecting to it. Pinch the hose when you are having the high idle condition. If the idle speed drops, there's a problem with the unit. Also check the electrical ground connections on the engine for looseness and oxydation.


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## mick (Dec 30, 2004)

My A.C. raises my idle 400 rpm. What would it be besides the F.I.C.D. solenoid?


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## matt_101 (Feb 5, 2007)

What do you guys think of leaving it unplugged and boosting the motor? I have been plugging it in when its cold outside - will that cause me problems under boost conditions?


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## OchnofConcrete (Jan 7, 2008)

dunno.

depends on the power of the boost i guess, the A/C comp will be keeping with the crank. you push it too far there's a chance you could wear it out faster.

i think the rpm comes up with the A/C on just to give the motor a little more power for the extra strain.


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## OchnofConcrete (Jan 7, 2008)

i'm not sure what else besides what you pointed out would alter the rpm just cuz the A/C is turned on.

there's usually only one accuator (meaning the dictionary use of the word), that effects any part on an engine. meaning, things generally aren't redundant. one thing does one thing.

if the F.I.C.D solenoid is what tells the ecu to alter the rpm cuz of the A/C, then that's probably the only thing that does that.

i don't know for sure, cuz all i've ever done with an A/C so far was rewire the compressor to the harness. i've never had A/C in my cars... wastes engine power.


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