OK, so I know someone that was getting a fairly frequent 420 code on their vehicle which means the bank 1 cat is not functioning as efficiently as it should be. The code would pop up every couple of weeks but the cat is not restricted and there are no performance issues. (he started by installing brand new O2 sensors)

So this guy saw on utubers where some guys claim catalytic converters can be cleans which he tried. I think he removed the O2 sensor temporarily so he could spray some Seafoam in front of the cat to let it soak in hopes it would clean the cat and take care of the occasional 420 code.

But after that the 420 code eventually came back although it took a little longer to do so.

So, he also saw on utubers where you can drill out an anti-fouler (normally used on really old engines so prevent spark plugs from oil fouling) and put that in the O2 sensor bung and then put the O2 sensor in the anti-fouler

When watching videos about this, it basically shields the O2 sensor from the direct flow of exhaust but is still reading the exhaust enough to supposedly satisfy the the vehicle's ECM to think there are no issues with the efficiency of the cat.

So this guy went thru all this and is telling people he fixed the 420 code issue and my question is... what is the drawback from doing this sort of thing verses installing a new cat?

I'm wondering if having an emissions test performed on the vehicle would be a good idea to see if the exhaust has more emissions than normal and to see if the air fuel mixture is within safe parameters. (we're in an area that does not require emissions, but one county over they do so getting an emissions test shouldn't be hard to do)

Seems to me there's got to be a down side of using an anti-fouler to shield the O2 sensor but maybe not. Seems like he should get an emissions test to verify that part of it is OK.

Just wanted to see what you guys think concerning using O2 anti-foulers... does it do anything to damage the engine by making it run too lean? Or too rich?

One of the utubers claiming this worked great for him said "The engine light will set when the cat is only about 95% efficient instead of 100%. That's why I've used them on my cars. If the code comes back with the spacer on, then the cat is very inefficient and needs to be replaced"

Here's the video from this utuber:

 

There is no functional problem with disabling, or rendering less useful (via anti-foulers), the rear O2 sensors. Those rear sensors are only there to monitor the cat(s), they do not have any impact on A/F metering nor how the engine runs. You could completely remove the rear O2s, cap the ports, and the engine would run exactly the same. The rear O2 & cat codes can be deleted with tuning (or an O2 simulator).

If you don't need to pass an emissions test then I can't see any reason to be concerned with this nor worry about taking a test "just to see" if it passes. It doesn't matter if it passes the test, in this case that's only a measure of cat function and not necessarily anything to do with how A/F is being metered. As long as the front O2s are functioning correctly and you're not seeing any rich or lean fuel trim codes, misfires, etc., there's nothing to worry about.

 

You can find O2 simulators online that replace the rear O2 sensors.

 

Great thanks!

That was the part I was wondering about, so I'll let him know he should be good to go.

So when guys run without cats, this is what they do... disable the rear O2 sensor?

I always wondered if there was a way to fine tune a vehicle to where it didn't need cats at all.

 

You don't actually have to disable it, you can just ignore the SES light if you don't have to pass an emissions test. I don't really recommend that though, as you won't know if any other codes are popping up since the light will always be on for a known issue. But you can disable the codes for the rear O2s and the cats via custom tuning or with O2 simulators (connected to the wiring harness). In either case, you can still leave the actual O2 sensors screwed into the sensor bungs or you can remove them completely and cap or weld shut those bungs.

No vehicle actually "needs" cats; in fact, they will run better (better MPG, more power) without them. Prior to 1975, nothing had cats in the first place. It's just an emissions piece, not anything that's necessary for proper operation of the engine or vehicle.

Or are you referring to the concept of tuning the car to where tailpipe emissions on a catless example would be comparable to a catted one? I don't see how that would be possible.

 

Someone on this site passed a sniffer without cats. Can't remember the username.

 

I think this guy's wife drives the vehicle most of the time so that's not going to work.


So it's not possible for 100% of the air/fuel mixture in each cylinder to be burned off?

 

The EPA Greenies want you to replace the cats soon as you see a MIL and have a code. But, the reality is they are still working they aren't producing as clean of air output as the feds want to see. If you can deal with a mil and the car runs fine and you don't have to pass a emmissions test just leave em alone as is. I've seen cars and trucks driven for years and another 100k plus miles with the lamp on and still running fine. If cash is an issue leave it alone as is wont hurt a damm thing as long as it's running fine.

 

No need to have a check engine light on the dash related to this issue.

Apparently there are ways to make the light go off