From a previous and now somewhat buried post...

 

I have an '02 2.5RS and am trying to find out:

 

What is "IAC?"

 

How can I locate the oxygen/MAF sensor(s)? (links to pictures would be wonderful)

 

Where can I find a good, or at least decent, maintenance manual?

 

Thanks again.

Hi,

 

While I'm not familiar with the specific model, here are a couple of answers to your questions:

 

IAC - Idle Air Control. This is the little motorized valve unit that controls the idle speed of the engine. It is essentially a computer-controlled valve that opens and closes rapidly, under the engine management's commands to vary the air allowed into the engine when the throttle is fully closed. That's why modern cars have such a rock-steady idle.

 

MAF - Mass Air Flow sensor. This should be located in the intake air tract. Start from the air box or air filter housing and work back towards the engine. You will find a block-like part with wires coming out of it. This unit senses the mass of air being swallowed by the engine and based on this (and other inputs), the computer opens the injectors for just the right amount of time to ensure a correct fuel/air mixture.

 

The O2 sensors (oxygen sensors) will be located in the exhaust tract, fairly close to the engine, usually, although some cars have upstream and downstream sensors on either side of the cat.

 

Hope that helps.

 

Regards,

Adnan

If you haven't already done so, get down to your local Auto Zone or Advance store and buy a Haynes manual for your car. They are usually very thorough with lots of helpful photos--about $15.

If you haven't already done so, get down to your local Auto Zone or Advance store and buy a Haynes manual for your car. They are usually very thorough with lots of helpful photos--about $15.

Thanks for taking the time to respond.

 

As far as I can tell, both online and in the stores, Haynes doesn't have anything for Subaru past '98. Do you know of any others?

Hi,

 

While I'm not familiar with the specific model, here are a couple of answers to your questions:

 

IAC - Idle Air Control. This is the little motorized valve unit that controls the idle speed of the engine. It is essentially a computer-controlled valve that opens and closes rapidly, under the engine management's commands to vary the air allowed into the engine when the throttle is fully closed. That's why modern cars have such a rock-steady idle.

 

MAF - Mass Air Flow sensor. This should be located in the intake air tract. Start from the air box or air filter housing and work back towards the engine. You will find a block-like part with wires coming out of it. This unit senses the mass of air being swallowed by the engine and based on this (and other inputs), the computer opens the injectors for just the right amount of time to ensure a correct fuel/air mixture.

 

The O2 sensors (oxygen sensors) will be located in the exhaust tract, fairly close to the engine, usually, although some cars have upstream and downstream sensors on either side of the cat.

 

Hope that helps.

 

Regards,

Adnan

Thanks for the clarification; turns out what I suspected to be an O2 sensor was the MAF. I need to get some pictures to clear up locations and descriptions of all of the components. Thanks again.