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Old 09-18-2010, 11:11 AM   #1
iRick.
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Join Date: Sep 2007
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Location: 2014 WRX
Default Very low idle and slight hesitation?

Here's the details:

2007 impreza.

had a full straight pipe with o2 sensors plugged in.

after a few weeks, CEL came on, figured it was because, obviously, the sensors caught on that there is indeed no CAT.

a few months later I finally got a catalytic converter, and a full exhaust.

after everything was installed, and the CEL was cleared, this is where it gets difficult:

car didn't want to start, after 2 attempts, it started. Since then, I've had no trouble starting it. But it has a VERY low idle. It died once, trying to slowly go over a speed bump, but since then... It runs fine, pulls fine, responds fine, just has a very very low idle, and requires a bit more gas than usual to initially leave from a stop.

is this simply because my o2 sensors are shot?
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Old 09-18-2010, 12:15 PM   #2
RaineMan
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running straight-pipe with O2 sensors plugged in may have fried them. But I'm thinking if they were reading out of range you would be getting a CEL.
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Old 09-18-2010, 12:25 PM   #3
05rs_will
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that seemed to happen to me a couple of times, i just disconnected the battery then after i reconnected it let the car idle for about 5-10 mins, i was told that this remaps the ecu.
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Old 09-18-2010, 05:23 PM   #4
yarrgh
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Quote:
Originally Posted by RaineMan View Post
running straight-pipe with O2 sensors plugged in may have fried them. But I'm thinking if they were reading out of range you would be getting a CEL.
Can't see how that's possible, at least on the upstream sensor, since it's pre-cat.

OP, reset your ECU, I believe the 2007's use the rear sensor for fuel trim as well.
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Old 09-18-2010, 06:37 PM   #5
J-Chow
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how low is your idle reading? My 06 2.5i requires a bit more gas to start from a stop, about 0.5 inch of depth on the gas pedal until the ECU reacts to my response.

I've been having crap idle after warm start ups. It would crank and rev up, then drop down to about 500/550 rpm and either a) stay there or stall or b) slowly increase to about 650rpm.

Do you have an aftermarket intake? I have SRI and I would blame it on that cause I have no tune so far. Either that or a shot o2 sensor. How's your spark plugs, and spark plug wires? Make sure all the wires have a flow of current going through.

I'm due for a timing belt change + water pump change as well, but I don't think that would affect idling issues.
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Old 09-18-2010, 06:51 PM   #6
RaineMan
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My normal idle is around 500. It does take some gas and RPMs to get moving from a stop, but that's b/c of the AWD and from what I understand is normal operation for this type of vehicle.
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Old 09-19-2010, 05:47 AM   #7
iRick.
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my normal idle is around 600. it was idling near death.

but, today, I turned my car on when it was already warm, and suddenly its driving fine, idling fine, no hesitation, no wanting to die..its back to normal. But my CEL is still on for o2 sensor. I guess that's the answer to my question right?
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Old 09-19-2010, 04:29 PM   #8
RaineMan
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If the CEL is on for your O2 sensor then that is what you need to get taken care of.
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Old 09-19-2010, 07:23 PM   #9
zigzag801
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the low idling happens all the time when you clear the CEL (or disconnect the battery). I have straight pipe on my RS and I get the CEL all the time with the cruise control blinking and everything (Need to get it tuned to get rid of it cause even spacers aren't helping) BUT anyways just disconnect the battery and let it sit for a few min, then reconnect it and turn the car on and let idle for about 10 min. Then go drive around, works for me everytime!
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