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Old 05-09-2008, 11:43 AM   #1
Mercureie
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Member#: 83995
Join Date: Mar 2005
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Location: Cleveland, OH
Vehicle:
2010 Jeep Wrangler

Default High idle and rpm surging after car sat for a while

Just started up the car for the first time in a while (~2 months) and it was driving fine for a bit then noticed a high idle (~1800) at a stop light. Then the rpm's started cycling between 1500 and 2000 rpm's.

I searched around but couldn't find anything about surging with this high of a range.

BTW, car is stage 2, w/ up-pipe


-Jon
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Old 05-09-2008, 02:16 PM   #2
socomcaptain05
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2004 WRX Stage 0
Aspen White

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is it getting warmer where you live? Because my car is doing the same thing, and I'm wondering if its just the fan trying to keep up with the heat. This is the first time I have had this car in hot weather, so I'm not use to the high idle either.
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Old 05-09-2008, 05:11 PM   #3
4wdrift
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99 RBP GC8 Impreza

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Hard to say whats wrong without actually being there listening to the car. Two months is
not that long though. I would try some injector cleaner in the fuel. and a new air filter
(if its old).
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Old 05-09-2008, 06:41 PM   #4
Mercureie
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Thats what I was thinking. I've not started it for longer periods than this, just seems weird.
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Old 05-09-2008, 07:30 PM   #5
Mercureie
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alright, so i just let it idle for a bit in the driveway and the surging didn't happen this time, but when the rpm's started to lower i noticed a slight dimming/flickering of the lights and interior gauges. could this be electrical? or is the dimming just a product of the engine struggling at lower rpm's?

needless to say I'm puzzled haha
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Old 05-09-2008, 09:30 PM   #6
4wdrift
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Subaru alternators have a notoriously weak output at idle. The dimming of everything is normal.
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Old 02-19-2009, 03:32 PM   #7
Vew
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2000 Outback Sdn

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Bringing back from the dead because I might know the answer since I had the same problem. Loosen your throttle cable that goes into your cruise control module. From what I understand what happens is that when you're sitting there idling, it heats up the module causing it to pull on the cable, bringing your RPMs up. When you get moving again, it cools down and releases it.
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Old 02-19-2009, 07:08 PM   #8
madmax718
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Vew, I hope thats it, cause it doesnt sound quite right.

Following your theory, the module heats up, pulling on the cable. Ok, lets assume that is true. Im just thinking that that would then result in a consistent rpm rise, not just an unstable idle.

Im leaning toward your MAF, or something to do with it.
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Old 02-20-2009, 01:41 AM   #9
scotty17509
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I had a little trouble like this a few months ago. Mine wasnt quite so high rpm, and it was surging a little more. What fixed my car was upgrading the ground cable. There is a post on here somewhere about this mod. I tried searching but couldnt find it. Anyway you may want to try adding a large wire coming from the battery to the engine and battery to the chassis.

I noticed a big difference not only with the idleing problem but also overall performance.
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