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2008 Forester X 2.0L
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Discussion Starter · #1 ·
Hello,,, hope someone can help me...

2008 forester X (2.0L) with 48,000 km, manual trans....

Well the problem began today, yesterday the car was ok.... when i turn on the A/C the revolutions of the cars drops below 500rpm (maybe 400, may be lower), when the A/C is off the Revs are ok (about 750rpm)....

if I drive with the ac on when i stop pressing the gas pedal the revs goes down almost to 0 rpm and then go up ti 450 rpm....

so i think that system that compensate the revolutions (idle) when the A/C compressor its on its broken (maybe a vaccum valve, a sort of sensor???),,,,

if someone can helpme would be grate...

sorry for my english its not my native language...

gracias
 

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2008 Forester X 2.0L
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67 Posts
Discussion Starter · #3 ·
Another thing that discover today... usually when I turn on when the engine its cold the RPMs stay at 1200-1500 (aprox) until the engine get hot.... now the car doesnt do that, the car turn on and the revs stay at 750 RPM, also it was difficult to start the car... the A/C was off



thanks
 

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There is a component; Idle Air Control Valve (IACV) on the throttle body assembly. It allows air to bypass the throttle plate and ECU adjusts idle speed to compensate for load and engine coolant temp; air temp etc.

When IACV is clogged w/ dirt/oil (from PCV reverse flow), the air can't get through the IACV and idle will sag below 750 when hot and load (AC) is added. IACV could also be faulty (bad solenoid), however this should set the Check Engine Light and have a code for IACV electrical fault. If you don't have a CEL, then dirty IACV is more likely. You may also need to clean the passages to/from the IACV.

good luck
 

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... Idle Air Control Valve (IACV) ... You may also need to clean the passages to/from the IACV. ...
I vote for that suggestion too -- good call. Juan Pablo, be sure to use only throttle body cleaner. Do not use brake cleaner. Some IACV's are teflon coated and a strong cleaning agent will strip off the teflon and invite worse problems. You can clean the throttle body too.

I wish I could tell you more about Subaru's IACV; my experience is with Mitsubishi's. Our Forester (U.S.) idles fine so I've never had to clean ours.

Good luck with your fix.
 

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04 Forester X, MT
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1,039 Posts
on the 2.5L N/A the IAC on the throttle body on the driver side near the clamp for the air cleaner housing. It has a bright blue label on it. UNISEA JECS with a number (or something close to that).

scratch that ... the IAC valve was only used on NA '98 through '04 I have seen here. so you probably have a different problem?! i'm not sure how the idle control is different on 05+. have you tried the "search" function here?
 

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2000 2 Outbacks 1Man , 1 Auto
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312 Posts
Hi There, On your model there is no IACV, the idle is controlled solely by the Powertrain Control Module which regulates the idle through an electronic control throttle system. So idle is controlled basically by the Accelerator Pedal position sensor (upper end of Pedal) and various other sensor inputs including one from the a/c control module via a pressure sensor and another from the a/c lock sensor whose input to the pcm is supplied via fuses in the main fuse box. Would check these fuses first.
 

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2008 Forester X 2.0L
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Discussion Starter · #9 ·
Thanks everybody for the replies and advices.....

I did the cleaning and seems to be working just fine :Banane08:, the throttle body was very dirty, now some pictures:

the body in the engine


removing it


dirty body




clean body


another time, thanks for the help guys!:Banane29::rock:
 

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2007 2.5X 5mt
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943 Posts
Just cleaned out my T/B. Mostly because i was bored and its nice out today. This is the first time I have seen a T/B with coolant passages in it. Thought that was interesting. I didn't think the T/B would get hot enough for that.
 

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2008 Forester X 2.0L
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Discussion Starter · #11 ·
Yes... for me was a little difficult to remove the coolant lines (big hands/small spaces) but at the end i did it, well the T/B was very hot too.... i have to say that doing that procedure was very easy
 

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04 Forester X, MT
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Just cleaned out my T/B. Mostly because i was bored and its nice out today. This is the first time I have seen a T/B with coolant passages in it. Thought that was interesting. I didn't think the T/B would get hot enough for that.
I think it's more for consistent temperature and emissions-related than to keep it from overheating.
 

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2007 2.5X 5mt
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I think it's more for consistent temperature and emissions-related than to keep it from overheating.
Question:

If the Throttle body and intake manifold are at the operating temp of the engine, How doles a "cold air intake" really make a difference if the air is collecting heat off the throttle body and intake before it even gets in the intake valves? There seems to be a bit of surface area in the manifold to transfer heat to the incoming air.
 
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