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HOW-TO: Mechanical CEL Fix for a Header

59689 Views 137 Replies 48 Participants Last post by  j_thielmann
7
Well, there's always threads on how a newly-installed header has caused the check engine light to come on. Here's a tutorial to circumvent this problem. A tune can disable your rear o2 sensors, but in States whose smog stations plug into the OBD-II port, a disabled o2 sensor will instantly fail you for smog. This is a mechanical fix; it does not turn off or disable any of your o2 sensors.

Tools required:
Strong drill
1/2" drill bit
Vise (preferably)
Crescent wrench
Anti-seize copper sealant
Jack and jack stands


1) First off, you need to check how many o2 sensors you have.









2) If you have THREE like in the picture, you will need to buy TWO packages of these:





There should be two anti-foulers in each package. Get these exact ones. You can find them at Pep Boys, Kragen and most auto parts stores. If you only have TWO o2 sensors in your exhaust manifold, then you will only need one package.






3) Now, you'll need a 1/2" drill bit, a vise and a fairly strong drill. Make sure your drill bit is sharp. You will need to drill a 1/2" hole using the drill bit through the anti-fouler, essentially opening up the hole that already present. For people that have THREE o2 sensors on their header, you will need to drill two of these anti-foulers. YOU NEED TO DRILL ALL THE WAY THROUGH THE ANTI-FOULER, OTHERWISE THE o2 SENSOR WILL NOT SCREW ONTO IT.










4) Ok, so now you will want to disconnect and unscrew the #2 and #3 o2 sensors from the car. For those that only have two o2 sensors, you only need to disconnect the last sensor. You'll need to jack up your car to access the #3 o2 sensor, so take car doing that. Put it under a jack stand or two.



5) Take one drilled anti-fouler and screw it on top of an un-drilled anti-fouler. Use some anti-seize on the threads. Now screw the #3 o2 sensor on top of the the drilled anti-fouler. Use some anti-seize on these threads as well, but don't overdo it and slop it all over the sensor. Screw this double anti-fouler assembly into the header bung, using anti-seize on the threads again. (For those of you that just have two o2 sensors, do this step for the #2 sensor; you are done)

It should look like this:










6) Now take the other anti-fouler you drilled and install that on the #2 o2 sensor, using anti-seize. Here's how it should look:





And just for clarification, do NOT put any anti-foulers on your primary o2 sensor. That one monitors your engine and has nothing to do with emissions. LEAVE IT ALONE!!








7) Make sure everything is tightened down. Unplug the battery for 10 mins. Plug it back in, lower the car from the jacks and take it for a spin. Hopefully you have the same luck as me and your CEL should not come on again.
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this works too...ive seen it in person. sick ass set up
very nice write up syz, good pics,easy to understand, perfect.
Nice write up man! looks pretty simple! [thumb]
But it could be that you make it look easier than it is too! lol
Good write up might have to do it. so a tune wont get me past the emissions?
It depends on which State you live in and the smog station.
cool! i was thinking bout doing this but didnt know how i would do it


thanks for the how to!

Jonathan
It depends on which State you live in and the smog station.
i ant gatta go till 2009 but its supposed to be done in 08 but than in 07 they said it would be done and its still here wat BS.. around here 7 countys make u do it the other dont so i dont see the point
really good write up, may have to do that when i get a header, dont plan on tuning for a while
how does this work in theory if you don't mind me asking? i'm just curious
Same as a normal o2 sensor you just need the anit-foulers because an o2 sensor will no fit into the header ocrrect me if i am wrong.
Same as a normal o2 sensor you just need the anit-foulers because an o2 sensor will no fit into the header ocrrect me if i am wrong.
nope.

from what i've read, it moves the o2 sensor out of the direct path of the exahust gas, making it read a lower level which makes your car think that the cat is still there and is cleaning the air.
nope.

from what i've read, it moves the o2 sensor out of the direct path of the exahust gas, making it read a lower level which makes your car think that the cat is still there and is cleaning the air.
This would be correct somewhat. What doesn't make sense to me is that the sensors only calculate the difference from the rear 2 sensors. So If I'm correct, you would only need the fowler on the rear most sensor.

Very nice write-up, I vote sticky.
I 2nd the sticky.
SYZ, this is a fantastic write up. great job. not a sticky, but a how-to, right?
Another Honda trick switched to the Focus scene. NICE writeup. There is another how to of this on Honda Tech I thought was cool. Original idea, and keeps that big O2 cheater from having to get ziptied up somewhere.
This would be correct somewhat. What doesn't make sense to me is that the sensors only calculate the difference from the rear 2 sensors. So If I'm correct, you would only need the fowler on the rear most sensor.

Very nice write-up, I vote sticky.

Well, the second o2 sensor is after the first half-section of the mani-cat, meaning it should read lowered emissions compared to the primary o2 sensor. That's the reasoning behind putting an anti-fouler on there. The third sensor should read very little emissions, and also see an additional difference between the emission levels of the #2 o2 sensor and the #3 sensor. That's why you want to pull the sensor further away from the exhaust flow. But if you pull it too far away from the exhaust flow, it won't read anything and the ECU will think the sensor is bad, triggering a CEL. So some people might have luck with drilling two anti-foulers and combining them together on that third o2 sensor if they are getting a CEL for a bad o2 sensor.
is there a certin size to get or no im going to do this sometime today and try and get my light to come off
do you think this method should work on a cosworth header? I can't even see the plugs for the sensors in their picture
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