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Discussion Starter #1
For last 3 weeks, my 2008 2.5i has been idling low and running rough at lower rpm. Then, few times CEL came up (with cruise light blinking) and then, it disappeared.
If I start the car and drive a right away, it gets low idling and runs rough. If I start it up and leave it for 10-15 min before driving, sometime it doesn't and sometime it does.

So, I checked the codes and got P0400, P0302, and P0303.
P0400 is EGR issue?
P0302 & 0303 is malfunction on #2 & #3 cylinders?

How should I tackle these issues? Replace spark plugs, wires, EGR valve? BTW, where is EGR valve? :) The car is 2008 2.5L with 200k miles.

Thanks in advance.
 

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Did you replace or disconnect the PCV valve lately?
I had that problem and discovered the original PCV valve hose was leaking where it plugged into the valve. It was tired. Moving it around a bit helped while I waited for the Subie parts dept to get a new one into stock. Changing that hose fixed it all for me.
 

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It is not unusual for EGR valve to stick open. This would cause EVERY symptom you are experiencing.

*) low idle
*) misfire on that side of engine
*) etc

A good test would be to disconnect the EGR valve and MAKE CERTAIN it is closed.
The idle issues should go away (the EGR code will obviously remain)

If the PCV valve was sticking open... the idle would be low... but the EGR codes would not be set.
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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Discussion Starter #5
Did you replace or disconnect the PCV valve lately?
I had that problem and discovered the original PCV valve hose was leaking where it plugged into the valve. It was tired. Moving it around a bit helped while I waited for the Subie parts dept to get a new one into stock. Changing that hose fixed it all for me.
Nope. I haven't touched PCV valve. Where is it located at?
 

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Discussion Starter #6
It is not unusual for EGR valve to stick open. This would cause EVERY symptom you are experiencing.

*) low idle
*) misfire on that side of engine
*) etc

A good test would be to disconnect the EGR valve and MAKE CERTAIN it is closed.
The idle issues should go away (the EGR code will obviously remain)

If the PCV valve was sticking open... the idle would be low... but the EGR codes would not be set.
oh.. EGR valve = PCV valve? <--- I found they are different part.
How do I check 'CERTAINLY' it is closed? Visual check?
if it is bad, does it need to be replaced or cleaned?

Sorry for obvious questions. Newbie for DIY and cars
 

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Discussion Starter #7
Sorry for delay responding.. I thought i'm getting notification of replies but didn't. Just subscribed and set notification for it.
I will try all the suggestions (if I get informed where PCV valve is first :) ) and get back to ya all.

another question, if O2 sensor goes bad, does code reader give a different code than P0400?
 

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Don't do any of that stuff! Mine did the same thing, all you have to do is remove the intake air box and clean the throttle body and the flapper thoroughly(with a rag, toothbrush and carb cleaner) and your problems will be over!!!!!
 

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Discussion Starter #9
Finally got back from long vacation and ready to tackle this issue.
The car still runs but runs very rough on low idle.
Based on eagleeye's post of Subaru Maintenance schedule above, I need to change plugs too. So, got NGK plugs and wires too.
I will go one by one and see what caused the issue. or just do whole **** thing at once and hope the issue to be gone.
 

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Discussion Starter #10
It is not unusual for EGR valve to stick open. This would cause EVERY symptom you are experiencing.

*) low idle
*) misfire on that side of engine
*) etc

A good test would be to disconnect the EGR valve and MAKE CERTAIN it is closed.
The idle issues should go away (the EGR code will obviously remain)

If the PCV valve was sticking open... the idle would be low... but the EGR codes would not be set.
Please help here.
'Disconnect' means disconnect the wires? or remove the EGR valve? Either case, how do 'MAKE CERTAIN' it is closed? How do I determine mine is bad? I see a lot of used EGR valves in Fleabay Is that ok to get used one or get it from Subaru dealer shop?
 

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Please help here.
'Disconnect' means disconnect the wires? or remove the EGR valve? Either case, how do 'MAKE CERTAIN' it is closed? How do I determine mine is bad? I see a lot of used EGR valves in Fleabay Is that ok to get used one or get it from Subaru dealer shop?
I meant to disconnect the electrical plug from EGR valve(to make sure it is not being commanded to open)

To make sure it is closed, try to blow air thru it and make certain it is not flowing any air when closed.

If EGR valve is stuck open.... it will feed exhaust gases right into the intake manifold. Obviously, exhaust gasses WILL NOT BURN so it makes the engine run awful.

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The PCV valve RARELY goes 'bad'... it is simply a spring-loaded check-valve. Just clean it (with carb-cleaner) once in awhile and it will last the life of the vehicle.

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EGR = Exhaust Gas Recirculation
PCV = Positive Crankcase Ventilation
 

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Discussion Starter #12
I meant to disconnect the electrical plug from EGR valve(to make sure it is not being commanded to open)

To make sure it is closed, try to blow air thru it and make certain it is not flowing any air when closed.

If EGR valve is stuck open.... it will feed exhaust gases right into the intake manifold. Obviously, exhaust gasses WILL NOT BURN so it makes the engine run awful.

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The PCV valve RARELY goes 'bad'... it is simply a spring-loaded check-valve. Just clean it (with carb-cleaner) once in awhile and it will last the life of the vehicle.

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EGR = Exhaust Gas Recirculation
PCV = Positive Crankcase Ventilation
I disconnected the wire but still runs rough. I wonder if the EGR valve is opened and doesn't get closed, disconnecting the plug wouldn't do any good. I don't have any way to test the EGR valve, I ordered new one and I will get it by this weekend. Then, I will find out for sure.

Few days ago, I did tune-up: Cleaned throttle body, Replace the air filter, Replaced spark plugs, and wires. I noticed oil were evidenced, especially driver side (2 & 4 cylinders) a lot, not on the plugs, above the thread. Must be leaking from that side of cylinder head gasket. But the error codes that I got was 1 & 3.
 

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Discussion Starter #13
Got it running smooth.

As brucep suggested, it was EGR valve. Once I replace with new one, the low idle roughness is gone. As others suggested, I did followings:
1. Replaced PCV valve,
2. Cleaned throttle body,
3. Changed spark plugs and wires

The above didn't fix the issue but it was due anyway.

Thanks all for suggestions and especially thanks to brucep.
 
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