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Old 01-12-2006, 09:55 PM   #1
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Default Antifouler / CEL Fix for Header

I'm doing this because there isn't a specific writeup, and we get WAY TOO MANY CEL FIX threads. Now, it should be even more easily searchable.

The purpose of this little mod is to fix the Check Engine Light caused by the installation of aftermarket headers. Aftermarket S-pipes will not cause this light to come on. There are several other fixes available commercially, but many of us aren't willing to pay $50 when this $3 fix works just as well, if not better.

I've had the megan header on for about 10 days now, and travelled over 300 miles. No CEL whatsoever. Gas mileage has not been affected, as far as I can tell. (I got 290 miles on a full tank, but have been flooring it excessivley to feel the new header)



Here's what you'll need-

1-Aftermarket headers installed on vehicle.
2- HELP brand spark plug antifoulers, 18mm, part number 42002. ($2.99 at most auto parts stores. I got mine at autozone.) You'll need one pack, which contains 2 antifoulers.
3- Drill with 1/2 bit able to cut metal. I used one designed for wood, and it worked fine.
4- Jackstands to lift vehicle, and tools (I used a wrench) to remove second o2 sensor.
5- Penetrating spray lubricant to help with sensor removal.

How-to

1- Raise the vehicle and secure it with jackstands or other methods of your choosing. I do not recommend using just jacks.

2- Locate the S-pipe, immediatley after the header. Locate the secondary O2 sensor sticking out of the S-pipe, which will be more towards the passenger side and slightly behind the horozontal plane of the axle.

3- Unplug the other end of the sensor, so that the wire isn't damaged in the removal. You'll see where it attaches, and its a simple clip. Use your tools and lubricating spray to pull the secondary o2 sensor out. THIS SENSOR IS CROSS-THREADED, you will be damaging the threads in removing it. Work it very slowly out, take your time, and limit the damage to the threads as much as possible. You'll want something left on there to keep your sensor in.

4- Take your drill with the 1/2inch bit and one of your antifoulers. Drill straight through this antifouler, widening the hole at the end and turning the antifouler into a straight little metal tube. This will take a while, and get quite hot in the process.

5- Screw your modified antifouler into the un-modified antifouler. Notice that you've created a little "chamber" for your O2 sensor, with a little hole at the end. This little hole will be exposed to the exhaust stream, and limit the amount of gas that the sensor sees.

6- Screw the sensor into the modified antifouler. Screw the whole assembly into the O2 sensor bung. It will look like this.

O2sensor > Modded Fouler > Unmodded fouler > O2 sensor hole.

7- Clear your CEL by either disconnecting battery or OBD-II tool, whichever you prefer. Be sure you plugged the sensor wire back into the electrical connection.



And enjoy your now CEL-free car!


If you still have a CEL after this-

1-Check your work, be sure you didn't install it incorrectly.
2- Be sure its the second sensor, NOT THE FIRST ONE THAT SCREWS INTO THE HEADER. The first sensor acts more as an A/F meter, and will throw off your power and gas mileage.
3- Be sure you didn't damage the sensor. This is common, and easy to do since the sensor is difficult and cross-threaded.

If all of this doesn't work, then you'll need to try something else. This solution will work over 95% of the time, and has been used for years in a number of different cars.
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Old 01-12-2006, 09:59 PM   #2
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Yep.. the anti-foulers have a price tag because a lot of people dont have access to the tools to do it themselves.. but those that can.. this writeup is great
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Old 01-12-2006, 10:08 PM   #3
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Good writeup.... Nice to have something so people don't need to pay 50 bucks for a lower priced fix.
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Old 01-12-2006, 10:28 PM   #4
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I'm sorry to disagree with the 95% thing but its more like 65-75%. Mine feel within the numbers that don't work. It might be b/c I have cai with s-pipe and a header so the flow is a lot more than that of a header alone. I am not sure but I used my laptop to datalog and the anti-fouler will not work with i/h/spipe setup! Sorry to say but this is true. If you want a good fix relocate the second o2 sensor on the midpipe behind the cat there and you will have no issues with aftermarket headers. I am using zpi midpipe and Magnaflow cat and resonator. The cat I bought is a 2.5" in and out carb cetified california emissions and has a o2 bung in it already. I will not have anymore cel problems b/c of the aftermarket header one I get these parts. I am just waiting on the midpipe with should have shipped so it will be complete soon.
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Old 01-12-2006, 11:10 PM   #5
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If what you say is correct, then the problem will be addressed later.


This does not detract from the usefulness of this fix. If it doesn't work, then you've lost $3. Big whup.

Let's try to keep things positive. This is working for me, is working for others, and will work for many people. I didn't spend 30 minutes typing that up to start arguments about its effectiveness.
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Old 01-12-2006, 11:18 PM   #6
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I didn't say that to start a argument. I just stating what I have found to be true. How many miles have you put on your car since? Do you drive interstates a lot and get past 80mph? I have notice if you keep it in the city the cel tends to stay off but once you get it on the interstate and have at least 200-300 miles on the car the cel pops.
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Old 01-13-2006, 12:10 AM   #7
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I have upwards of 4000 miles on my anti fouler with no CEL. Ive had K&N CAI, stock airbox, Injen SRI, Injen CAI, stock s-pipe and CC s-pipe and have not had a CEL since the day I installed my header and anti fouler at the same time. Ive done city driving, Vegas road trips, open track racing and everything in between with no problems at all. I am proof that the anti-fouler mod CAN work perfectly even though others cant get it to work no matter what they do.
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Old 01-13-2006, 01:04 AM   #8
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About 300+ miles, including a 50 min highway/interstate trip to the track, racing at the track, and 50 min back.

There's probably another factor involved that's causing yours to pop. What it is, I have no idea.
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Old 01-13-2006, 01:30 AM   #9
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^ I agree as well.... I have thousands of miles CEL free with my antifouler after not having success with O2 Sims....

And my engine has all kinds of fun modifications... and does all kinds of things....

I really think there is another factor where people have antifouler failure...
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Old 01-13-2006, 09:03 AM   #10
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What header do you have to start with and what midpipe do you have. I belive and aftermarket header and zpi s-pipe flows really well causing the cel. I have the Alphawerks header and it tested the highest gains. Also the s-pipes 02 bung location might throw it off also. I am aware that the s-pipe alone will not cause a cel, its caused by the aftermarket header not having a cat.
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Old 01-13-2006, 11:59 AM   #11
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It's not going to matter which header you work with.

The ZPI S-pipe would work even better with the antifouler mod, due to the relocated sensor.

I'm sorry it didn't work for you, but this doesn't mean it won't work for the average joe who's looking to try quick fixes before dropping 15x more cash for yet another error-prone method.
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Old 01-13-2006, 01:35 PM   #12
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The system compares the readings between the O2 sensors both before and after the Cat. If there is no difference, or not enough, then the Cat is either not there (in the case of a header) or not working. The antifouler trick moves the second 02 out of the stream a bit, thus causing a difference in reading. If you look at the $50 fix thats out there, it is simply an exaggerated version of the anitfouler. It is longer to move the 02 further out of the stream. I am not sure if there is room, but if you did the antifouler trick correctly and it did not work, maybe try three of them.
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Old 01-13-2006, 02:53 PM   #13
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The ecu actually has specific voltages that it looks for in the sensor. Its not really comparing the two. It is making sure the voltages are within set parameters and if doens't then the cel will set.
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Old 01-13-2006, 03:05 PM   #14
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Is it possible people who are getting CELs with antifoulers are having too little flow being picked up by the second O2 which is causing the ECU to beleive the pre-cat is clogged?

Just a thought...
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Old 01-13-2006, 03:16 PM   #15
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mods need to sticky this please!!!!

Lots of people are looking for a good explanation
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Old 01-13-2006, 03:20 PM   #16
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Sorry to say this but the too little flow is wrong! I have a laptop and datalogging capablility. I used this to log with and actually if you were getting little exhaust that wouldn't be a problem. The problem is getting too much emissions and causing the cel! I know this from datalogging a stock tc and one with aftermarket exhaust system!
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Old 01-13-2006, 03:26 PM   #17
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I was just offering that as something to look into that may have been previously overlooked. What are the parameters the ECU needs to see in order to not throw a CEL? Is there a high and low value that triggers the CEL?
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Old 01-13-2006, 04:19 PM   #18
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I believe that may be the case with the antifouler mod and individuals still getting a cel....

that the antifouler takes it too far out of the flow for that setup and it trips the CEL as a result.... there has got to be a fine line of where the sensor needs to be placed... I'm pretty sure those still getting a cel are on the too little flow side of it, than getting too MUCH flow with that setup.

But, who really knows..... I'd just play with it both ways until I got it to work.... at the price of an antifouler, you can make three or four different setups, before equaling the price of the other mods on the market.
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Old 01-13-2006, 04:48 PM   #19
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Quote:
Originally Posted by The_Instigator
I was just offering that as something to look into that may have been previously overlooked. What are the parameters the ECU needs to see in order to not throw a CEL? Is there a high and low value that triggers the CEL?
Yes there is a high and low value. I don't know exactly the value but if its lower than .015 it will set the code. And yes my problem was caused by too much flow. The anti fouler would work if you keep the rpm below 3500 when you hit 4000 the voltage spikes and over a period of 40-500 miles it will trip it. Don't get me wrong the antifouler trick may work for you its a hit and miss thing. It will either work or not work.
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Old 01-13-2006, 06:07 PM   #20
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Quote:
Originally Posted by toyota_scion_tc
Sorry to say this but the too little flow is wrong! I have a laptop and datalogging capablility. I used this to log with and actually if you were getting little exhaust that wouldn't be a problem. The problem is getting too much emissions and causing the cel! I know this from datalogging a stock tc and one with aftermarket exhaust system!
No one said it was 100% flow.. by moving it out of the flow you are reducing the amount it "sees" resulting in a lower reading in the second sensor. It doesnt just look at the threshold reading on the second sensor either. By having that, plus the values from the first sensor, you can tell if the CAT is doing its job. At least this is how I have seen it work on other vehicles.

The best setup (and the only one I would pay $50 or more for) would be a simple simulator. All it takes is a little bit of time to figure out the relationships between the 02 sensor readings and the normal operating voltages. You then develop the simulator circuit to read one sensor and apply the correct signal to the second one to simulate what the system expects to see. Maybe I should make this a future project along with the others I have But, I am pretty sure they have some decent ones out there, I just never looked for them.
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Old 01-13-2006, 06:07 PM
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