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How to fix iacv - Civic Honda Cars & Trucks

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IAC --idle air valve

Replace it -if cleaning doesn't help for awhile

Posted on Apr 30, 2014

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What is iacv


Hi Gui4540186,
IACV means Idle Air Control Valve.

Apr 30, 2014 | Honda Civic Cars & Trucks

Tip

Idle Air Speed Control valve on engines



1.4) IACV Idle Air Control Valve - Idle Speed Control Unit(actuator)

What is it? The idle air control valve is an electrically driven mechanism that allows additional control over the throttle at idle.

Where is it located? The IACV is located on or near to the throttle body and consists of a small device with an electrical connector.

How does it work? When the throttle is closed the throttle plate closes offair from the inlet manifold and normally this would cause the engine to stall immediately. To allow the engine to keep running the ECU makes use of the IACV system to permit the ingress of a limited amount of air. The IACV device is seen in two forms either a) a small motor driven valve on a passageway allowing air indirectly to pass to the inlet manifold plenum or b) a motor located on theTPS assembly that opens the throttle plate by a small degree to allow air through directly. Both systems are designed to allow air to by-pass the 'closed' throttle plate to maintain engine idle. The IAC also helps throttle respond to additional power demands being made on the engine such as using the power steering, air conditioning or moving the (automatic) transmission selector into 'drive'. Somecar manufacturers also have a separate 'hot idle' valve system and this is designed to operate for a relatively short period just during engine warm up. Such hot idle systems are accompanied by electrically driven IAC valves to maintain engine idle in the face of additional power demands.

Symptoms of faulty IACV
Associated OBD2 error codesDTCs: P1508, P1509

  • Poor starting, sudden stall: If the IACV fails to open or the inlet/exit ports are clogged shut with oily deposits the engine may ignite and then promptly stall. The engine can be kept running by pressing the accelerator. However any additional demand on the engine such as power steering or putting the car into drive (automatic) will cause the engine to stumble badly or stall.
  • Engine stall at stop sign: Even with the engine is warmed up, if the car comes to a halt such as a stop light the engine may stall. The engine will often restart immediately with little trouble

Thisdiffers from:-
a) TPS fault - engine stall when theaccelerator is depressed quickly, but will often restart without much trouble.
b) CKP or CMP fault - engine cuts out without warning and is resistant torestart until cooled down

How to check? Physically remove the IACV, keep the electrical connection and examine the state of the valve for carbon build up. Blank off the exposed IACV port(s) on the throttle body and turn the engine on; you may have to give it extra throttle until the engine has warmed up. Monitor the IACV valve movement in response to additional loads (power steering inputs etc) the valve should open and close according to demand. When refitted this action results change in engine speed in response to increased power demand.

The electrical connector to the IACV can have 2 or 4 pins:-
2pins: resistance between socket pins should about 10 OHMS +/- 3 OHMS. If this resistance is very high then there is break and the IACV is at fault.
4pins: resistance between diagonally positioned pins should be about 20 OHMS. If the resistance is very high this indicates that the IACV is faulty.

Resistance between the actual metal valve body and either of the socket pins should be greater than 10,000 OHMS. If there is little or no resistance thenthere is a short and the IACV is faulty.

How to fix? If the motor of the IACV has failed (no movement and fault resistance values) then replace it. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with WD40 or carburettor/choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IACV look dirty again clean them out thoroughly.


NEXT 1.5) TAC Throttle Actuator Control

on Jul 15, 2011 | Mercedes-Benz E-Class Cars & Trucks

1 Answer

1999 dodge durango 5.2l code po505


P0505 - Idle Control System Malfunctionxicon.jpghttp://engine-codes.com/p0505.htmlForum CodePossible causes- IACV-AAC valve harness is open or shorted
- IACV-AAC valve poor electrical connection
- Faulty IACV-AAC valve

Read more: http://engine-codes.com/p0505.html#ixzz1zVJIt34L

Jul 02, 2012 | 1999 Dodge Durango

1 Answer

How do i know if the iac valve is bad


Disconnect the iacv and if the idling performance doesn't change from what you are experiencing then it may not be turning or the passageways are clogged and need to be sprayed out with cleaner.

One can test the continuity of the iacv to see if it is within specifications using a multimeter.

One can turn the a/c on and if the car stalls, then the iacv may not be working.

Good luck on this diagnosis.

Jan 01, 2011 | 1998 Chevrolet Blazer

1 Answer

Car has in a fuel injected 1500 cc engine ,hard to start and uneven idle usually jump from 1500 to 3000 rpms when it should be idling


You probably have a bad Idle Air Control Valve (IACV). If it does not control the idle correctly , you can find yourself driving 50 MPH with out touching the gas pedal. The IACV is located on the throttle control valve and is typically held on by two or three small screws. The price for an IACV can run from $25 to $500. I purchased a throttle body for $40 , removed the IACV, and saved $400.

Dec 19, 2010 | Mitsubishi Lancer Cars & Trucks

1 Answer

2000 chevy tahoe z71 5.7 v-8 vortec intermittently wont start unless I spray starting fluid in the throttle body ! fuel pressure checks good on the fuel rail and I already replaced fuel pressure regulator...


I can think of four things. Do each in turn and test the engine after completing each one. If it gets fixed early in the list avoid the items later on. 1) check that your throttle interior is clean 'like new' along with the idle air control valve.
2) Idle Air Control Valve IACV - How to check? Physically remove the IACV but keep the electrical connection to it and loosely blank off the ports to the throttle inlet assembly, exposed by the IACV removal. Turn the engine on and examine the IACV valve movement in response to additional loads (power steering inputs etc). The valve should open and close according to demand causing perceptible change in engine speed with increased power demand being made on the engine.

The electrical connector to the IACV can have 2 or 4 pins:-

2 pins: resistance between pins should about 10 OHMS +/- 3 OHMS. Resistance between either of the pins and the valve body is greater than 10,000 OHMS

4 pins: resistance between diagonally positioned pins should be about 20 OHMS
How to fix? If the motor of the IACV has failed then replace it. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with carburetor choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IACV look blocked again clean them out thoroughly
3) Throttle Position Sensor TPS - How to check? The socket for electrical connection with the TPS has 3 pins, one for 'ground', one for 5 volts 'reference' and a third (generally the middle one) for 'signal' output. Back probe the signal pin in the connector to the TPS. Attach the positive lead of a voltmeter to the probe and measure the voltage output as the throttle plate is rotated. If working correctly the meter should show a voltage consistent with the throttle position from approximately 1 volt when closed and 5 volts when fully open. What is looked for is smooth voltage increase with throttle change. If there are drop outs in the transition or that there is no transition seen the TPS is faulty.

How to fix? If the track is dirty causing drop outs, try cleaning it with residue-free electrical cleaning spray. If the track is worn it is perhaps easiest to replace the complete device. In some instances it may be possible to adjust the location of the central mount of the TPS contact arm along the throttle shaft by a few millimeters and in the process cause a fresh concentric region of



4) Fuel pressure regulator _ Yes I know you have checked it for pressure but at start up when the ignition is at position 2 the fuel pump starts up and pressurizes the fuel rail. As you turn to position 3 "ignition" power is cut to the pump and fuel pressure is maintained by a non-return valve in the pump. If that valve is faulty the fuel pressure in the rail will drop to zero just when you need it and no fuel can be injected. Check the fuel pressure when at position 2 and then switched off; fuel pressure should be maintained for up to 5 minutes with little or no loss. If there is pressure loss then either the non-return valve is faulty or you have leak in the fuel pressure regulator. If it is such a leak, fuel will dribble from the vacuum line connected to it when disconnected.

Nov 25, 2010 | 2000 Chevrolet Tahoe

1 Answer

My rpm are very low car cut off unless i hoid the gas and no engine check ligth on .


Make sure the throttle body interior and throttle plate are clean and then check both the 1) idle air control valve and the 2) throttle position sensor:
1) Idle air control valve - How to check? Physically remove the IACV, keep the electrical connection to it and blank off the port to the intake plenum. Turn the engine on (you will need a little accelerator pedal pressure to keep her running) and examine the IACV valve movement in response to additional loads (power steering inputs etc). The valve should open and close according to demand which when fitted would cause change in engine speed with increased power demand made on the engine.

The electrical connector to the IACV can have 2 or 4 pins:-

2 pins: resistance between pins should about 10 OHMS +/- 3 OHMS. Resistance between either of the pins and the valve body is greater than 10,000 OHMS

4 pins: resistance between diagonally positioned pins should be about 20 OHMS


How to fix? If the motor of the IACV has failed then replace it. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with carburetor choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IACV look blocked again clean them out thoroughly.



2) Throttle position sensor - How to check? The socket for electrical connection with the TPS has 3 pins, one for 'ground', one for 5 volts 'reference' and a third (generally the middle one) for 'signal' output. Back probe the signal pin in the connector to the TPS. Attach the positive lead of a voltmeter to the probe and measure the voltage output as the throttle plate is rotated. If working correctly the meter should show a voltage consistent with the throttle position from approximately 1 volt when closed and 5 volts when fully open. What is looked for is smooth voltage increase with throttle change. If there are drop outs in the transition or that there is no transition seen the TPS is faulty.



How to fix? If the track is dirty causing drop outs, try cleaning it with residue-free electrical cleaning spray. If the track is worn it is perhaps easiest to replace the complete device. In some instances it may be possible to adjust the location of the central mount of the TPS contact arm along the throttle shaft by a few millimeters and in the process cause a fresh concentric region of track to be used.

Nov 19, 2010 | 1996 Ford Explorer

1 Answer

Have 1988 honda civic that is surgeing while in park


The surging is related to your Idle Air Control Valve (IACV), it adjusts idle based on coolant temperature, your coolant could be low or your IACV could be bad.

Jun 20, 2010 | 1998 Honda Civic

1 Answer

I have a 1989 accord lxi with 130000mi. the idle started fluctuating from 700-1600 rpm when the engine is warm and has been driven a while, sometimes i can get it to stop by reving the engine. i cleaned...


generally cleaning the idle air control valve does not fix the problem, because the dirt or carbon deposits causing the problem is not were you can see it. It usually is in the valve stem and housing and you cant get it clean like it needs to be. Replace your idle air control valve and this will fix your problem

Oct 11, 2009 | 1989 Honda Accord 4 Door

2 Answers

The car starts and immediately stalls unless I


Hey Jruthesq

The 850 is equipped with an Idle Air Control Valve (IACV) which supplies the engine with air when idleing (a necessity since the main throttle body valve is completely closed when no throttle is applied, thus the engine would lack air without the IACV when idleing). The IACV is suspended in a rubber mount on the front of the throttle body itself, and is easily removed and inspected/cleaned. If it's dead a good cleaning usually gets it going again. Also make sure that the air from the IACV is unhindered on its way from the IACV to the throttle body (it's actually common for the holes in the throttle body to be gunked up so bad by hardened carbon deposits that one sometimes needs a nail or even a drill to open it up again).

Just thought I'd mention this since you said that the gas needs to be feathered for the engine to start. When you press down on the gas the main valve in the throttle body opens up, closing the IACV and supplying the engine with enough air.

Oh and if your fuel pump relay is a green one marked 103 you should replace it with the new and improved red one. The relay is located under the fuse box cover under the hood. Remove the 4 torx srews holding the cover in place and you'll see the relays under there.

Good luck mate!

Jul 01, 2009 | 1997 Volvo 850

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