AFR sensor/rough idle
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This is a discussion on AFR sensor/rough idle within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Ive only had my WRX for a few weeks its an 05 Ckeck engine light was on and I had ...

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    AFR sensor/rough idle

    Ive only had my WRX for a few weeks its an 05 Ckeck engine light was on and I had a friend check it, it said air/fuel ratio sensor was bad, I haven't had a chance to replace it yet, but my question is would that affect the idle because my car idles real rough, when I come to a stop it almost stalls but never does or is that a completely different problem that needs addresed. 05 wrx it has an aftermarket intake and cat back exhaust and manual boost control

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    Pro Manscaper Mikie13's Avatar
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    Bad AFR sensor is the least of the worries, but could lend to rough idle.

    What kind of an intake? My hunch already is that it's an Injen, which is a POS and is known to cause problems.

    Where my concern now lies is with the MBC. Do you not have a proper tune on the car? If you don't, the previous owner probably jacked up the boost which could be a potential problem. I'd get the car checked out by a tuner ASAP.
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    Re: AFR sensor/rough idle

    ^ what he lukie13 said.
    +my old car acted the same way when it's sensor failed.

    Posted from a fone.
    Last edited by UEDan; 12-13-2012 at 01:57 PM.

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    Pro Manscaper Mikie13's Avatar
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    lukie13?
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    the intake is a little frankensteined spt filter and pipe the filter is on the rest is perrin and the boost control is also a concern of mine because there is no boost guage so I have no idea what its doing any suggestions as to who I should get to check it out anyone in the York Pa area

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    Pro Manscaper Mikie13's Avatar
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    Take some pics and post them up! I wanna see how bad this thing is hacked up.

    There's a couple good places down in Maryland. Couple in NJ if you are willing to travel.

    But yeah otherwise, I'd find a stock setup as fast as I can if I were you. Stock airbox and stock boost control solenoid/system...whether through a dealer or used on Nasioc classifieds, etc.
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    didnt get a chance to snap any pics today and I'm out of light but I certainly will do that and what kind of damage can an intake do

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    Pro Manscaper Mikie13's Avatar
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    well if you're just jacking boost up with an MBC, you're adding more air, but the ECU doesn't know to add more fuel since it isn't tuned for it and it isn't what's controlling the boost. You could be running very lean which can lead to knock and blowing up an engine. Yes, its worst case scenario, but it's happened before, ergo why it's generally frowned and warned upon.
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    AFR sensor/rough idle

    Quote Originally Posted by Mikie13 View Post
    well if you're just jacking boost up with an MBC, you're adding more air, but the ECU doesn't know to add more fuel since it isn't tuned
    That is not quite how it works. The ECU knows to add fuel because of the MAF sensor. The problem lies with the Openloop fueling delay and the higher load values.




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    Re: AFR sensor/rough idle

    Quote Originally Posted by Donkey View Post
    The problem lies with the Openloop fueling delay and the higher load value
    Yep. Anything that puts you into a higher load cell needs to be tuned. That's anything that changes/improves the VE of the motor. An MBC alone set to the same boost to which the EBCS was tuned may put the motor into higher load cells at a lower RPM range since the turbo is spooling sooner, but it will unlikely cause knock at higher RPM unless the target boost has been changed.

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    Thanks for all the info I guess a tune needs to be in my near future because if I'm spending money on the wrx I would rather be making it better not going backwards with performance. It seems I have a lot to learn about this vehicle

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