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Old 06-23-2005, 03:22 PM   #1
CrazyMike13
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Default Problems with my catless exhaust (CEL Related) HELP!

I've had a catless exhaust for over 6 months now and I was used to the CEL codes I was getting. Well, I finally got an MIL Eliminator that I thought would take care of the codes. I thought wrong.

I'm getting a misfire on ALL 4 Cylinders and a problem with the front 02 Sensor. The CEL pops up ONLY when i'm at idle.

I have COBB CAI, Borla Headers, Custom track pipe, and an Apexi N1 exhaust along with a lightened flywheel.

Does anybody know what could be causing these cylinder misfires and what I can do about them?

Any help is appreciated.

Thanks!

-CM!3
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Old 06-23-2005, 05:33 PM   #2
tmeh
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maybe the sensor has finally bit it?

i had front and rear 02 fail codes with my brullen equal+high flo cat+tanabe race pipe and changed the front 02 sensor, then next time the MIL came it was just the rear fail.
if that could go bad enough to cause misfire i'll let somebody else diagnose.

front 02 is upwards from the cat right, so catless or not shouldn't affect it alot...

maybe the wiring for the MIL eliminator is causing more problems
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Old 06-23-2005, 06:38 PM   #3
CrazyMike13
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Well, I was getting misfires before the MIL so, i'm sure that's not what's CAUSING it, but if the front 02 is failing and CAUSING the misfires, then that would definitely explain it.

Does anybody know if the 02 sensor can cause misfires?

-CM!3
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Old 06-23-2005, 06:42 PM   #4
impr25rs
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I am not fully sure, but I would not be suprised since the front O2 sensor controls the A/F raito, and if it's FUBARDed, it would create the wrong ratio for the engine to run on. Then that can cause misfiring, or "limp mode"
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Old 06-23-2005, 07:19 PM   #5
karl_hungus
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I had the same problem and I have similar setup to yours but Brullen headers instead of Borla.

With those mods your car runs very rich so the 02 sensors will fail prematurely. I now make a point of replacing my front 02 sensor almost annually, might be overkill but I am a bit paranoid. I've replaced the front 02 twice now and I have not seen any misfire or lean condition codes since.
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Old 06-23-2005, 08:39 PM   #6
Tim Sanderson
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How many miles on your car? Have you ever replaced the front air/fuel sensor? Have you ever replaced the rear o2 sensor? How are your plugs? how about your fuel filter?

I had the p0420 intermittently from 70k till 120k miles. I changed both my sensors and all is good.

I can't help with the misfire code, sorry.
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Old 06-23-2005, 11:00 PM   #7
CrazyMike13
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70K+ miles, never replaced the front air/fuel sensor, plugs are new and new fuel filter.

So it looks like i need to replace the front 02 sensor?

Thanks for all the help so far!

-CM!3
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Old 06-24-2005, 02:12 AM   #8
tsubaru02
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cats suck huh
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Old 06-27-2005, 01:24 AM   #9
CrazyMike13
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BUMP cause i'm about to purchase an 02 sensor and not sure if that's what I need!

-CM!3
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Old 06-28-2005, 01:08 AM   #10
The Anti Riced
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if i understood correctly, you aren't running a catalytic converter? why?
do you have any idea what you are doing to our breathing air/ environment?
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Old 06-28-2005, 04:31 AM   #11
Nicklbrso
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Quote:
Originally Posted by The Anti Riced
if i understood correctly, you aren't running a catalytic converter? why?
do you have any idea what you are doing to our breathing air/ environment?

This has nothing to do with what he's asking. Leave your own personal beliefs out of this.

Mike,

I would replace the front O2 sensor if it has never been changed w/ 70K miles.
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Old 06-28-2005, 09:26 AM   #12
Texas25RS
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I am not going to read the whole thread... so let me post...

My car did this same thing when I replaced the clogged up stock cat with a RT high flow. Within a few days my front O2 took a dump and so much gas was being dumped into the cylinders, the spark plugs simply could not ignite the mixture. I replaced the front O2 sensor (which can be done without getting under the car) and everything is fine... just back to the same old 0420 CEL...
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