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Old 11-15-2012, 05:55 PM   #1
zoltan
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Default Strange symptoms - bad battery?

My car is having some strange symptoms and I hope you can help diagnose it. This morning the car wouldn't turn over and it needed a jump. After that it drove fine.

This evening I cleaned the terminals and battery posts. The first time I tried to start the car just cranked for a couple seconds. The second time it started up. I took it for a test drive, and several times after driving 35+ mph the engine died as I was coming to a stop. Several more times the engine almost died, but caught and stayed running.

I have a 2008 Impreza which still has its original battery (4.5 years old), so I suspect it's a bad battery. However, these aren't the symptoms I've seen for a dying battery in the past.

Any ideas?
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Old 11-15-2012, 07:20 PM   #2
Duvanator
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sounds like the battery, my factory battery went out last winter on me (also own a 2008)

the car almost dieing on you is because the batter didn't have enough juice to turn the car over, and died, it probably caused the ecu to reset. the car can have sporadic idling and wanting to die when you drive it right away after reseting the computer. which it sounds like is what happened. it is the computer trying to adjust all it's ratio's and re-learn different things related to your driving and the surrounding atmospheric conditions
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Old 11-15-2012, 07:50 PM   #3
cal_look_zero
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Keep it simple, go to autozone/napa/oreillys and have them test it. Even with a bad battery, the alt should keep the car running while driving. You may have more issues.
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Old 11-15-2012, 11:02 PM   #4
zoltan
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Autozone tested the battery and said it was bad. I've installed a new battery but it's still having some idle issues. The engine hasn't died, but it's still letting the idle drop too low when I put in the clutch after driving 35+ mph. Hopefully it's just the ECU relearning the car. I figure if it's not running normally after I get home from work tomorrow then I'll take it to my mechanic.
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Old 11-15-2012, 11:07 PM   #5
Duvanator
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what i've been told is that after the ecu is reset (new battery) it is best to start the car and let it idle for 10-15 minutes to learn/ set up what it needs to.

I to had the crazy low idle, and stall once or twice when i depressed the clutch while driving. happened after i had the battery disconnected for a period of time. just keep driving it and it should correct itself. those issues only ever happened during the first 100 miles?
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Old 11-16-2012, 07:16 AM   #6
zoltan
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So I found the idle reset procedure Duvanator mentioned in another thread and tried it. I turned the key to on for 30 seconds, turned it off, and then started the engine and let it idle for 10+ minutes without touching anything.

After that it was good to go.

EDIT: Before I did that, though, I disconnected the battery again for several minutes to reset the ECU again.

Last edited by zoltan; 11-16-2012 at 08:30 AM.
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Old 11-16-2012, 07:28 AM   #7
Duvanator
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thats good to hear! I know it scared me and I though it was something major when it happened
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Old 11-16-2012, 09:24 AM   #8
treksofar
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Another thing to check is to see if you have gunk built up around the butterfly valve in the throttle body. For a while, whenever I reset the ECU or did a battery pull the car would have issues returning to idle for a few days. If there's excess gunk in there the ECU needs more time to learn how much to crack open the valve for a smooth idle.
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Old 11-16-2012, 11:26 AM   #9
gdoggmoney
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Clean all of your ground cables, and replace them with copper ended cables that are proper sized. The factory grounds are horrible, worse than a VW.
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Old 11-22-2012, 09:42 PM   #10
Ralph47
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Is there a DYI for removing the throttle body or is it self explanatory? I have some rough idle issues and cleaning the TB in my old dakota helped a ton, I have other things I am going to do first but figured I could add this to the list if those do not work.
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Old 11-22-2012, 10:55 PM   #11
rhino6303
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Pretty self explanatory. Remove coolant hoses, disconnect electrical connections and remove the 4 bolts. You should replace the gasket upon re-install.
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Old 11-23-2012, 12:39 AM   #12
Ralph47
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Fair enough, more work than my truck but still sounds easy enough. Thanks
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