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Old 05-21-2001, 02:59 PM   #1
Peaty
Techno Sapien
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Member#: 449
Join Date: Oct 1999
Chapter/Region: MWSOC
Location: Lawrence, KS
Vehicle:
2019 Impreza Sport
Lithium Red

Question Erratic idle when cold

I've recently put a new K&N panel filter in my 99 RS(I had an older K&N in there that belonged to our OB). After I installed it I disconnected the negative on the battery for about a half hour-45 min. Started it up and let it warm up till the fans kicked on. The idle was pretty erratic bouncing from 2K or better to almost stalling. I didn't want to touch the gas while it was hunting so I just let it go till it finally settled to it's normal 700 RPM or so. Then I put the car away for the night. The next day I started the car and it did the same thing again but this time it stalled. Now whenever the car is cold started it gets close to or almost stalls. I did the reset with a warm motor does that matter? It seems like the ECU didn't reset properly. I plan on doing it again letting the car sit overnight w/the battery disconnected and the motor cold. Once the car has warmed up it drives fine with a normal idle. I've checked to see if any vac hoses came off or wires but everything seems normal. My Vac gauge reads fine too so I don't think it's leaking vac anywhere. Any ideas why this is erratic idle is happening or did I just do a bum job of resetting the ECU? I've driven around quite a lot so I thought it would have taught itself by now even if I didn't do the reset. Any thoughts?

Peaty
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Old 05-21-2001, 06:25 PM   #2
Revision
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Hmm.. Sounds like a bad temp sensor in the radiator.
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Old 05-21-2001, 06:37 PM   #3
Rich L
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Custom Rallispec kit/IC#1

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You MAF might be dying.
to confirm this...
After start up, let the engine warm up just a little. While the engine revs up and down, disconnect the MAF and the car will go into limp home mode.

If the idle smooths out after you disconnect the maf, then chances are thats the problem.
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Old 05-21-2001, 08:41 PM   #4
Peaty
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Lithium Red

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Thank for the ideas I'll have to check both out.
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