The ECU of a modern vehicle is a wonderful thing: it determines transmission shifts, engine timing, and an array of other things, including monitoring many other modules for consistency. Fortunately (or unfortunately) depending on how you look at it., O2 spacers negate that function – or help it, depending on where you stand.
If you stand for ‘the earth’ and are very interested in the gases your vehicle outputs, you won’t like these little baddies whose sole purpose, right from the moment they were thought out and left the forge, is to be to defeat emission control.
However, if you don’t know what ’emissions’ are or could care less (for any reason whatsoever) and instead, will prefer to have a clean cluster, devoid of CELs, then, the idea of an O2 sensor will certainly excite you.
Article Outline
What Are Oxygen Sensor Spacers?
Oxygen sensor spacers (also known as O2 spacers) are threaded adapters, usually stainless steel, and meant to go into the exhaust bung where the O2 sensor would otherwise thread in.
The O2 sensor, in turn, threads in on the prior attached O2 spacer, creating a ‘space’ between the exhaust pipe and the oxygen sensor itself, hence the name, ‘spacer’.
The intent of this ‘adapter’ is to create some form of distance between the exhaust bung and the O2 sensor itself…this ‘space’ is what helps trick the ECU and ultimately, assists the O2 sensor spacer achieve its intended aim.
But, how exactly is this aim achieved?
How Does an O2 Sensor Do Its Thing?
When an internal combustion engine runs, it draws in air (oxygen) and fuel, which is mixed and burnt up in the combustion chambers to create power and propel the vehicle.
After that happens, the resulting gases, usually harmful, are channeled into the catalytic converters (via the exhaust ports) where with the help of numerous precious metals there, a chemical reaction takes place and these gases are ‘converted’ into less harmful gases, including steam and water.
Now, most catalytic converters are designed with two oxygen (O2 sensors) on their bodies: pre and post the respective catalytic converter.
The pre-catalytic O2 sensor measures the content of oxygen in the exhaust gases going into that catalytic converter. The post-catalytic O2 sensor measures the oxygen content in the exhaust gases after passing through the catalytic converter.
Remember that the O2 spacer attaches to the exhaust bung and effectively increases the distance between the oxygen sensor and the expelled exhaust gases.
This unique attribute of it is going to come in handy in the next section where it’s all going to make sense, if it hasn’t, already.
How the ECU Decides (When to Set a CEL)
The ECU monitors the content of the combustion gases, indirectly via the pre and post-cat oxygen sensors.
What the ECU does when it takes signals from these sensors (especially the post-cat oxygen sensor) is to compare the oxygen content from the readings of the post-cat O2 sensor to the content of the oxygen the pre-cat O2 sensor registered.
If or when the oxygen content the post-cat O2 sensor sees is insignificant or the same as what the pre-cat O2 sensor reports, the ECU determines that the catalytic converter on that bank isn’t doing its job and accordingly, sets either the P0420, P0430 (or both) CELs, indicating the challenge.
By creating a physical distance between the O2 sensors and the exhaust, the exhaust gases are forced to travel further than they would, with most of the oxygen content lost in the process.
The result? The oxygen content in the exhaust gases now differ between the output of the pre and post-catalytic converter oxygen sensor, with the output of the post-cat sensor being appreciably lesser.
The ECU reads this and concludes that the respective catalytic converter is doing its job and sets no CELs.
Are O2 Spacers a Quick Fix for Bad Catalytic Converters?
If you’ve ever been faced with either a P0420, P0430 (or both), you don’t need anyone to tell you just how stubborn these CELs are. Cleared, they come back, usually, after just one drive.
If you choose to ignore them, you won’t have any idea when and if other issues come up, issues that need attention and should be handled.
If, on the other hand, you choose to clear the codes, it’s going to be a serious task, one you’ll need to indulge in daily, and for that purpose, you’ll certainly need a dedicated glove box code reader.
The solution, either way, is to figure out a way to permanently take out the CEL, which boils down to replacing the defective catalytic converter(s) or getting a spacer to temporarily sort the issue.
So, are O2 spacers a quick fix for bad catalytic converters? To fully answer that question, I’ll need to explain the types of damage a catalytic converter typically passes through.
Chemical vs. Physical Damage: How a Catalytic Converter Goes Bad
A catalytic converter usually goes bad in one of two ways: chemically or physically. In very rare instances does it go bad in both ways.
When a catalytic converter goes bad chemically, it remains great, physically, but loses its ability to ‘convert’ harmful exhaust gases into relatively safer gases. Looked at with the naked eyes, a chemically bad catalytic converter is hard to tell.
However, the fact that the relevant CEL(s) keep(s) being illuminated is conclusive evidence of it/them having gone bad. This type of damage is rare, but occurs, nonetheless, especially with catalytic converters that haven’t been properly taken care of.
On the other hand, a physically damaged catalytic converter is easy to spot or discern. The honeycomb mesh usually collapses, obstructing the flow of exhaust gases. On physical inspection, it’s easy to conclude what’s wrong.
That, a spacer be used for a cat-related code largely depends on whether the cat is physically or chemically damaged.
So, should you do O2 spacers?
Wrapping Up: Should You Do O2 Spacers?
It depends. On what?
Simple: it depends on whether your catalytic converter has been damaged physically or chemically (which you can only decide when you’ve taken the cats off the motor and physically examined them).
A physically compromised cat should not be ‘patched up’ with an O2 spacer (the collapsed internal honeycomb-like structure will obstruct the flow of exhaust and ultimately, ruin the engine).
However, if a catalytic converter is only chemically damaged (i.e. still intact but no longer ‘converting’ exhaust gases), a spacer may be a good idea – if used as a temporary measure.
However, it’s important to know and understand that global warming is real. It’s therefore important to play your part, no matter how seemingly small, in keeping the earth safe.
That said, it’s a crime in some jurisdiction to use an O2 spacer, especially when done with the intent to manipulate emission tests. Before you consider using an O2 spacer, check with your local authorities to ensure you’re not breaking any laws by installing it.
Finally, understand that even if it’s perfectly legal to use O2 spacers in your jurisdiction and your cat is only chemically damaged, it’s important to understand that it’s only a temporary measure: nothing beats a vehicle with good, functioning cats, not even a shiny O2 spacer!