How to lower your Car"s NOx Emissions and also Pass Smog inspect

I lower my NOx emmisions by 234 PPM

By rob Cockerham | September 8, 2019

Last May, I acquired ready to sell my car, yet wasn’t able to acquire past the to plan stage since I’d need to pass California Smog check in may be to offer it. CA Smog check tests five things: %CO2, %O2, Hydrocarbons, Carbon Monoxide and Nitrogen Oxide.

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A tiny shop well-known as a Smog inspect Station experiment my car running on a dynometer in ~ 15mph and also 25 mph. It to be tested below all the emission maximums, other than for when it pertained to Nitrogen Oxide. Wherein the legal border for NOx emmision in ~ 15mph is 459 components per million, my car was placing out 583 components per million. This was a FAIL, which intended that I had actually to take action to deal with this car, so the it polluted less.


High Nitrogen Oxide readings reveal a “too lean” burning situation, wherein too lot air and not sufficient fuel space making it into the piston cylinder for burning. This can result in an unusually hot combustion, which creates the undesirable NO. NOx is created when the engine temperature is over 2500 F.


My prompt reaction to be “oh crap, now I have to buy a brand-new catalytic converter. They are so expensive, and also this car has two, and I won’t even be permitted to install it myself, crap.” yet I didn’t really understand if purchase a catalytic converter was the exactly solution. To be there anything rather I could do? Unfortunately, the perceptible test equipment is only available at Smog check stations, for this reason I’d require to examine my outcomes with an additional $60 test every time ns tried other new.


I figured ns would try a few things on my very own first, climate splurge for a mechanic’s deal with on the second try. On the various other hand, every cheap fix felt favor it could be a finish waste that money.


Here’s what ns fixed:

1. I readjusted the spark plugs. This cost about $8 and only took around 15 minute to swap the end for new. Spark plugs have actually a call for being amazing at sparking when then space new, however then settle in together a little less sparky as they acquire old. Anyway, they to be cheap, therefore why not?

2. Ns ran a tank of supreme higher-octane gasoline with the car. I read something about high-octane gas dissolving or cleaning deposits or some crap, so ns tried this.

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3. I addressed a wheel bearing. I had one wheel grind a little. I had read part Smog examine advice the advised making sure your tires are effectively inflated, and maybe also OVER inflated to aid with the dynometer test. Because the engine is actually pushing the wheels as soon as tested in ~ 15 and also 25 mph, any resistance to the wheels running smoothly is do the engine work-related harder, and that’s most likely to do the emissions higher. This was a the majority of work since I had actually never readjusted a wheel bearing, however the car needed it, so i can’t reprimand smog check. On the other hand, if ns couldn’t acquire the car to pass smog, ns wouldn’t be able to register or offer the car, so the new bearing would be money and time wasted.

4. Ns sped approximately for 20 minute on the freeway on the method to the smog check. This heated up the car, the catalytic converter, climate engine, the suspension, the interior, eveyrthing was hot. Probably this pains the test, or probably this helped. Who knows?

Great news! other worked, because I pass the test!

A few months later on I was ago at smog check, and also my NO score at 15 mph dropped indigenous 583 ppm (parts per million) come 349 ppm! This was listed below the legally mandated 459ppm maximum! ns passed! currently I deserve to sell the car…. Or drive it myself, or stash a sweetheart chest in the trunk…