NO, you don't use foulers on the primary O2.

The primary O2 sensor is there to read the A/F and adjust the timing/fuel to the engine accordingly.

The secondary O2 sensor only has ONE function. This is to tell the ECU that the catalytic converters are there, and they are working properly.

The secondary O2 reads the A/F and it wants to see a change in the reading the primary O2 got. When you eleminiate the cats, there is no change, and that will trigger a CEL. However, put the non-fouler in there, it makes a change, and the engine doesn't know the diffrence. This is NO WAY SHAPE OR FORM EFFECTS THE ECU'S ABILITY TO CONTROL THE A/F RATIO.

This is true for ALL OBDII cars. Not just ours. Yes, I am sure.

 

Also, you actually need 2 non-foulers for each side. I don't remember the part numbers, maybe Eldy can chime back in here and help us out with that. But I have done this to like 3-4 G35's now with much success. I've ran this on my car for close to a year now and about 15-20k miles later. No probelms at all.

 

Kansai makes perfect sense. The nonfouler only contstricts the flow of gas passing over the sensor...but it does not reduce the amount of impurities that will reach the sensor (eventually).

I have done and been using the non-foulers and I have still set off the SES light. It's probably cause to sensor being poisoned. I put the car through a lot of extremeties with track day practices and at our driver clinics, taking passengers around our track, and showing them the lines. so you'd figure that I'm flowing gasses with great velocity and still intering the small hole in the foulers. So I just let the SES light stay on..I check on it periodically to see if there's any other codes behind the O2 faults. Under regular driving..the SES light would never come on...only when I'm teaching/driving at the track I'd set off the SES. More so, I'd rather it be running a little rich than running dangerously lean.

 

Yes, its true. The O2 sensor reads the percentage of impurities in the exhaust gas, not the total amout of impurities. So on paper, it would seem the non-foulers would not work. All the non-foulers really do is reduce the amount of exhaust gas that the O2 gets to see. This in no way changes the percent of impurities, just the overall amount of exhaust gas.

However, since the non-foulers were so cheap, I decided to give it a shot. And it actually worked. Again, I mention I have had these on for almost a year now, and have traveled about 15-20k miles without any problems or lights going off. This also includes many track events, and still nothing.

 

so then what is the easiest solution if the CEL keeps coming on? Spark plugs, spacers, etc???

 

^ Using the non-foulers like this entire thread is talking about.