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Old 09-21-2005, 10:28 AM   #1
Jericho99
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Default idle low when AC is off

Hi everyone,

Just bought a 2000 2.5rs manual and noticed that the engine idles around 400 when AC is off but when it is on it looks to idle correctly at around 700-750. Is this a major problem? I would think that this would be the opposite, reset the ECU a possible solution? Any feedback would be great.

Thanks.
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Old 09-21-2005, 10:46 AM   #2
Calamity Jesus
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Yeah, reset the ECU.. and check for any possible vacuum leaks. Then start the car and watch as the idle sets itself.
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Old 09-21-2005, 02:45 PM   #3
newbiescooby2.5rs
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i have the same issue except mine is a 01 2.5rs AT. There are no mods on it, just stock. It hovers at 400rpm then stays around 500rpm when its cold out. AC isn't on though...is low rpm bad? Also, wouldn't ur ecu learn after a few weeks where it should be at? i was thinking 700-750rpm is normal.

oh i just changed my o2 sensor and it stopped surging and hesitating, would this cause the low rpm mentioned in jericho999's post?
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Old 09-21-2005, 02:55 PM   #4
Subie Gal
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AC runs on vacuum.
of course the idle will change when the AC is on
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Old 09-21-2005, 03:12 PM   #5
svek
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doesnt the tach start at 500 rpm?


and if you watch my temp gauge, when you turn the ac compressor on the temp goes up

Last edited by svek; 09-21-2005 at 03:19 PM.
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Old 09-21-2005, 06:13 PM   #6
jasona
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Never heard of anyone complain their idle is too low...
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Old 09-22-2005, 01:26 AM   #7
Aphex28
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You can't be idling at 400 RPM... the last ticks aren't to scale really.. the Tach starts at 500 RPM...
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Old 09-22-2005, 10:09 AM   #8
Jericho99
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It idles around the middle of 0 - 1 on the tach or just below, so that would be normal? I thought it would be more of about one tick below the 1?
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Old 09-22-2005, 10:27 AM   #9
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The line below the "1" is actually 750 but many people mistake that mark for 500. If your idle speed were really that low the ECU would set a trouble code and turn on the CEL.
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