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03 OBW stumble at start-up


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5 replies to this topic

#1 Brokechump

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Posted 24 August 2005 - 10:28 AM

Just added a 03 Legacy OBW to my stable, it's only got 48k mi and it's a MT behind 2.5L. If it's cool or hasn't been started in a few days it stumbles on start up. No CEL light, so looking for ideas.

When you kick it over, the rpm jumps above 1g then falls to around 3-400 and bounces up and down a few times then will idle smoothly and run great. My wife says that when the ac button was on it fired up and then died. After a two start-die tries it stayed running and quickly smoothed out. Any ideas?

What's the cold air valve and where's it located (found that in one of my thread searches) Any help is appreciated as always!

-Dan

#2 subiefan

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Posted 24 August 2005 - 07:19 PM

Hmmm.... Very interesting. My '93 Impreza does the EXACT same thing. I don't have a good idea as to what's causing it though.

Do you mean idle air control vavle? Sounds like that could be the cause. I am suspecting that with mine, because if you just give it a touch of throttle and start it, it doesn't stumble. As to where it is, I don't know that. My Chiltons doesnt cover your year.

#3 1 Lucky Texan

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Posted 24 August 2005 - 08:32 PM

Some folks have a habit of depressing the accelerator pedal while cranking/starting. It has been mentioned that this habit can confuse the ECU as it is trying to record some kinda minimum TPS position. Try to confirm your foot is not pressing the gas pedal during starting and see if that makes any difference.

just a guess - but HEY!, that's what you asked for!

Carl

#4 subiefan

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Posted 25 August 2005 - 03:00 PM

I'm pretty sure I'm not pressing the gas pedal when starting. Just to be sure, would pulling the negative battery cable reset the ECU just in case it has learned some sort of bad habbit?

#5 RallyKeith

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Posted 25 August 2005 - 03:10 PM

I'm pretty sure I'm not pressing the gas pedal when starting. Just to be sure, would pulling the negative battery cable reset the ECU just in case it has learned some sort of bad habbit?


That wouldn't hurt. Subaru's do have very smart ECUs and they do learn certain things like global/general ignition timing. Give it a try.

Keith

#6 Brokechump

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Posted 26 August 2005 - 11:12 AM

Sorry about that I dropped off....thanks for all the ideas!

Nice thought on the gas pedal...I can see how the ECM would get a false position. I definitely don't hit that on these new fangled cars...now my carbed cars get the stomp! But I'll try to reset the ECM this afternoon.

I'll check my 00 FSM pdf files and see if I can find the idle air control valve? The weird thing is it's just a start up thing, and only a momentary start up thing...otherwise she runs well. But that could point to a funky ECM initial setting or MAP that quickly gets sorted out. I'll find out!

Gracias! I'll repost when I figure this out...

-Dan




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