[Bunch of questions...]

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.

[Bunch of questions...]

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?

[Bunch of questions...]

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.

[Hesitation, Stalling and Dying]

Thanks all for your advice. I changed the air filter two days ago, and this seemed to help a bit. After checking the security of all of the intake ducts to the air filter unit, the noise under the hood is decidedly more of a growl when accelerating. Is that what all of those different ducts do; tune the noise? Anyway, I'm a bit of a neophite when it comes to looking under the hood. What is IAC? How can I locate the front oxygen sensor? Can it be replaced without going to the dealer (one tiny little dealership, one huge conglomerate, neither do I really trust)? Wouldn't the CEL be on if the sensor was bad? Where can I find a good, or at least decent, home maintenance manual? Thanks again.

[Hesitation, Stalling and Dying]

My '02 Impreza 2.5RS has developed a problem. At highway speed it has a tendency to lose power, then recover. When starting from a stop, it "hiccups" several times before settling into a relatively smooth acceleration. At idle, it slows from 1100rpm to 600, then back to 1100, then to 500, then 1100, then 400, almost dies, back to 1200, and if I let it go long enough will eventually die. The hesitation and stalling during acceleration and at speed are worse if I let it do its idle dance long enough (as after being stopped at a light). I found that the hose connection to the air filter assembly was loose, although I've never touched that, and the air filter had a good amount of "oily" residue (just replaced it) and an unexplained hole, like a rock had gone through the filter. Originally I thought it was water in the fuel filter, as with my first '84 1600 sedan, but that is unverified at this point, as, without a manual, I can't locate the filter. Further, I've read on this site some post re: MAF contamination and the resulting mixture problems. Any thoughts or advice would be appreciated.

 

Stan