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Subaru Idle Air Control Valve

05/22/2017 10:51 AM

Greetings!

I have a '95 Subaru SVX with a 3.0L, 6 cyl. Boxer engine, AWD, that I bought some years ago as a beater car for my daughter. A nifty little car if I could get it to run right. The engine lacks all power on acceleration and will not idle without dying. It is throwing up (OBD1) codes for Mass Airflow Sensor and Knock Sensor. Replacing these didn't improve the situation, still having the same codes. I finally towed it to a Subaru dealer for a diagnosis, and they recommend to change the Idle Air Control Valve, and quoted me a new valve costing more than the entire car is worth! With a fair amount of skepticism, I just took the car back home to do more research, hence my post today. So my question to any knowledgeable Gurus is if it is fathomable for the ECU to throw these types of codes without throwing one for the IAC valve itself? If it is, I would be more willing to shell out for a new valve to get the car back on the road. Thanks in advance!

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#1

Re: Subaru Idle Air Control Valve

05/22/2017 10:58 AM

I had a problem like that ages ago on a Citroen? (ex company car). Anyhow it had been taken to the main dealer plenty of times and they couldn't fix it.
Ignore the computer codes and all that cr4p. Go old school take all the air intake/fuel control stuff to bits clean it properly and reassemble it. In my case a tiny air passage was blocked with gunk and the damn thing just wouldn't idle.
These days, if the diagnostics can't identify it the average "mechanic" is lost.
Del

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#13
In reply to #1

Re: Subaru Idle Air Control Valve

05/24/2017 12:18 PM

Similar Chevy S10 TBI 2.8 Liter, hesitation on accel, all the sensors TPS, MAP, twice over for good measure, finally found a carbon rod deposited in toothpick size sensing passage under throttle body, didn't even replace the gasket under the throttle body, good for another 200,000 miles until a deer got in the way.

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#2

Re: Subaru Idle Air Control Valve

05/22/2017 12:08 PM

Try replacing the gas cap.

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#3

Re: Subaru Idle Air Control Valve

05/22/2017 1:05 PM

I have a 2003 Honda Odyssey that had symptoms pointing to the IAC. I took it off and cleaned it, bought a new gasket and put it back together. Problem solved.

That may not resolve your problem, but it's an expensive thing to do which might help.

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#4

Re: Subaru Idle Air Control Valve

05/22/2017 1:37 PM

What's the big deal, just trade it in on another beater...that's the beauty of junkers, if they can't be fixed cheaply and/or easily, you just get another one....

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#5
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Re: Subaru Idle Air Control Valve

05/22/2017 2:09 PM

Yeah, the engineer part of me gets that. It's more of a sentimental thing. It's my daughter's "baby" and doesn't want to part with it. She even named it "Fritz" (German name for a Japanese car????). She's Daddy's little girl, so I had to at least try. Told her that I'd give it this one last try, and after that the scrap yard will be called to pick it up.

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#6
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Re: Subaru Idle Air Control Valve

05/22/2017 3:42 PM

Yes I'm always amazed how quickly the old much loved junker is forgotten once the shiny new junker appears....Bless their fickle little hearts....haha

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#7
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Re: Subaru Idle Air Control Valve

05/22/2017 6:58 PM

Two of my daughters still have fond memories for each of their first junkers, even after they bought much nicer cars. One named her Mark III Jetta, "Jetty" and the other named her Mark IV Jetta, Bridgette. I think they wear their nostalgia glasses when they think of them which is understandable when you think that this first vehicle is their first object representing real independence. They bought them with their own money, titled in their own name and paid for their own insurance. Rite of passage. We never put any of our kids on the parental insurance policy. And they didn't drive our vehicles either. Too much financial risk there.

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#8

Re: Subaru Idle Air Control Valve

05/23/2017 1:40 AM

You could always buy another one, raid this one for spares and then scrap the remnants, couldn't you?

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#9
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Re: Subaru Idle Air Control Valve

05/23/2017 7:32 AM

Good idea, and thought of going that route too, but these cars are hard to come by and this is the only model that this particular engine is used on. They have a collector following. As I understand, there were only about 1800 imported to the states during the time they were made.

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#10
In reply to #9

Re: Subaru Idle Air Control Valve

05/23/2017 7:55 AM

It is best not to constrain any problem beyond the point where only one solution remains.

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#11

Re: Subaru Idle Air Control Valve

05/23/2017 11:51 AM

With both these codes, I would check for a wiring harness problem that is causing a poor signal back to the ECU. Check along the harness for a wear mark that may have worn through the wires.

The MAF sensor will set a code if there is a vacuum leak. Don't know what the response is to the MAF sensor code if the changes the ECU may make would cause the engine to run and set off the Knock Sensor.

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#12
In reply to #11

Re: Subaru Idle Air Control Valve

05/23/2017 2:59 PM

Good call , cleaning all the wiring chassis earth points is a good idea too.
I did that on my Nissan Micra and solved some really irritating central locking problems.
Del

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