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- Jun 5, 2007
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Recently I have noticed a lot of new threads been posted about idle problems and often the IACV seems to be the culprit so to help diagnose the problem as been IACV related or not I have gathered some info together about the IACV which may help people.
IACV= Idle Air Control Valve
The IACV is an integral part of the idle control system. It changes the amount of air bypassing the throttle body in response to a current signal from the ECU in order to maintain proper idle speed. After the engine starts, the IACV opens for a certain time. The amount of air is increased to raise the idle speed about 150-300 rpm. When coolant temperature is low, the IACV is opened to obtain the proper fast idle speed. The amount of bypassed air is also controlled in relation to the coolant temperature.
When Check Engine light is on. With the service connector jumped, CODE 14 is indicated, OR, scan tool indicates DTC P1508. It is highly likely a fault relating with the IACV.
The IACV is a component whereby when faulty is the most probable cause to most idle-linked problems. The problem can be symptomatic and may not even trigger the Check Engine light. The list goes:
•When cold fast idle out of spec (1,000 - 2,000 rpm)
•Rough idle
•When warm RPM too high
•Idle speed is below specified rpm (no load)
•Idle speed does not increase after initial start up
•On models with automatic transmission, the idle speed drops in gear
•Idle speed drops when air conditioner is ON
•Idle speed drops when steering wheel is turning
•Idle speed fluctuates with electrical load
•Frequent stalling while warming up
•Frequent stalling after warming up
Test you can do using a ohm-meter:
When the two terminals on the IACV are measured with an Ohm-meter, it must vary between 8-15 Ohms. If not, the IACV must be replaced.
Cleaning The IACV
If your car is struggling to maintain a idle and feeling like its going to stall when releasing the accelerator the IACV screen filter may be clogged with dirt.
How to remove and clean: If you have a front strut brace it's easiest to work on the IACV by removing it. I also remove the air intake pipe for more room and to clean port on throttle body from which air flows to IACV. The IACV is located at rear of intake manifold as shown in image below. Start by removing the 2x 12mm bolts. Next you will need to remove both coolant hoses place a cloth under iacv as some coolant will spill out when you remove these. Using a pliers squeeze the clips and slide them down along the hoses. You can now pull the hoses free from iacv. Last step of removing the iacv is to disconnect the connector plug.
Using some spray cleaner i.e carb cleaner spray inside the two holes. Continue to do this until no more dirty fluid comes out and the screen filter is completely clean. Once you’re done cleaning out the IACV let it air dry for approx 20mins.
I also spray some cleaner thru the port inside throttle body which directs air to IACV.
Reassemble:Follow reverse order of removal.
IACV= Idle Air Control Valve
The IACV is an integral part of the idle control system. It changes the amount of air bypassing the throttle body in response to a current signal from the ECU in order to maintain proper idle speed. After the engine starts, the IACV opens for a certain time. The amount of air is increased to raise the idle speed about 150-300 rpm. When coolant temperature is low, the IACV is opened to obtain the proper fast idle speed. The amount of bypassed air is also controlled in relation to the coolant temperature.
When Check Engine light is on. With the service connector jumped, CODE 14 is indicated, OR, scan tool indicates DTC P1508. It is highly likely a fault relating with the IACV.
The IACV is a component whereby when faulty is the most probable cause to most idle-linked problems. The problem can be symptomatic and may not even trigger the Check Engine light. The list goes:
•When cold fast idle out of spec (1,000 - 2,000 rpm)
•Rough idle
•When warm RPM too high
•Idle speed is below specified rpm (no load)
•Idle speed does not increase after initial start up
•On models with automatic transmission, the idle speed drops in gear
•Idle speed drops when air conditioner is ON
•Idle speed drops when steering wheel is turning
•Idle speed fluctuates with electrical load
•Frequent stalling while warming up
•Frequent stalling after warming up
Test you can do using a ohm-meter:
When the two terminals on the IACV are measured with an Ohm-meter, it must vary between 8-15 Ohms. If not, the IACV must be replaced.
Cleaning The IACV
If your car is struggling to maintain a idle and feeling like its going to stall when releasing the accelerator the IACV screen filter may be clogged with dirt.
How to remove and clean: If you have a front strut brace it's easiest to work on the IACV by removing it. I also remove the air intake pipe for more room and to clean port on throttle body from which air flows to IACV. The IACV is located at rear of intake manifold as shown in image below. Start by removing the 2x 12mm bolts. Next you will need to remove both coolant hoses place a cloth under iacv as some coolant will spill out when you remove these. Using a pliers squeeze the clips and slide them down along the hoses. You can now pull the hoses free from iacv. Last step of removing the iacv is to disconnect the connector plug.
Using some spray cleaner i.e carb cleaner spray inside the two holes. Continue to do this until no more dirty fluid comes out and the screen filter is completely clean. Once you’re done cleaning out the IACV let it air dry for approx 20mins.
I also spray some cleaner thru the port inside throttle body which directs air to IACV.
Reassemble:Follow reverse order of removal.
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