5 Tips to Avoid Failing a Big-Rig Emission Test

February 27, 2019

Just like your favorite holiday comes around every year, so does maybe one of your not-so-favorite government stipulations to drive a vehicle; the emissions test. And regardless if one feels it’s another governmental strong-arm, or a true help for the planet to keep the air we breathe a bit cleaner, the emissions test is a requirement where failing is not an option. On occasion however, failing does happen, and when it does, the vehicle owner is required to comply before legally able to move forward, both figuratively and literally.

Emission testing checks all of the onboard emissions systems from the EGR system, the diesel particulate filter system, and diesel exhaust and fluid system on the vehicle. Big-rig testing takes place with a “sniffer,” measuring the opacity output of the engine’s exhaust at the stack. The testing agency is also in search of any solvent-particular matter such as black smoke and soot being dispersed into the air.

The difference between a personal day-to-day car and a commercial diesel truck testing typically comes down to the differences in the fuel, with automotive spark ignitions running on gasoline and big-truck combustion based on compression-ignited diesel fuel. The testing practices for on-road diesel pickups are similar to that of the larger-duty trucks as well. Caleb Matzke of Matzke Diesel (Monroe, WI) notes that standardized enforcement is becoming more prevalent in the commercial logistics sector, in continued attempts to help keep our air cleaner. Matzke mentions that “with the massive amount of vehicles on the road, compliance in testing supports the same goals. We all live on the same planet and have to breathe the same air. It’s the only planet we have and the emissions produced, regardless of spark or compression ignited vehicles, can create a real hazard.” The issue came to light in the 1970s with continued attention ever since.

Matzke says, “with particulate matter and soot output over the years, well into the 1990’s, we witnessed the development of smog in many urban areas. Emissions testing is the process for us all to do our part, keeping our countries running, but doing so with a concentration on clean air.” With the standards and systems now in place, Caleb states “the reduction of solid output and the Nitrogen Oxides (NOx) from commercial diesel engines has been reduced by leaps and bounds. Today’s air consists of far less pollutants than where we would have been, without the proper systems in place.” For diesel-based manufacturers, the federal government mandated a tiered system of emissions control that started taking place in 1998, with adjustments along the way in 2004, 2007, 2010 and 2013. Matzke says “post-2010 diesels are now rolling off the line with exhaust output virtually as clean as the air going in.”

With any mechanical system however, failures can happen, breakdowns can take place and especially for emissions, contaminants can be reintroduced back into the system causing a failed test and worse, a complete shutdown of your truck. Following are a few tips to help avoid the undesired issues:

    1. Check your soot output. If your truck is putting out black smoke, you may be in violation of overage in soot output. Matzke says an easy test is to wipe the stack. When you see a black fingerprint on your hand or a buildup of soot on the rag, there is something amiss in the  regeneration system, where the soot and carbons are incinerated.


    1. Be aware of your check engine light. Fuel systems are very “smart” in monitoring every piece of every operation in the system. When something goes wrong, addressing the alert on the dashboard as quickly as possible. Doing so can very often help reduce the pending magnitude of the issue.


    1. Take advantage of additives. Fuel and oil additives in diesel engines help reduce carbon emissions, rust and corrosion in the system, and improve savings at the pump. Matzke recommends the use of fuel system treatments for many of his customers. “We highly recommend the Hot Shot’s Secret Everyday Diesel Treatment to our customers,” he says. “We have also implemented at our shop, the addition of HSS additives at every service interval. With the lack of lubricity quality contained in today’s ultra low sulfur diesel fuel, we’ve seen HSS product provide a significant uptick in the lifespan of injectors and high-pressure pump systems. By adding product to help keep the upstream components in good shape, the results transfer downstream as well, so that emissions components such as the diesel particulate filter (DPF) and EGR systems remain in good shape too.”


    1. Follow recommended service schedules. Caleb states it’s one of the best ways to succeed in compliance with emissions regulations, and avoid unnecessary expenses and downtime. “For example, the filter and the oxidation catalyst will last a very long time when serviced properly. Keeping the components in check in the vehicle’s exhaust gas recirculation (EGR) system provides a tremendous advantage in keeping your truck on the road.”


  1. Avoid idling time. In some areas it’s even a law to turn off the engine when not in operation. But even where it is not law, a diesel engine running at idle can cause hydrocarbon absorption (a composite of cordierite, silicon carbide, or metal fibers) in the DPF. Matzke explains “the filter and the oxidation canals will actually absorb the raw diesel fuel rather than it mixing, reacting and combusting to burn off the soot, creating a heavy load (failure) condition.

Matzke mentions in conclusion to “take the time to do these little things.” With the vast complexity in fuel systems, simply paying attention to your maintenance schedules and taking advantage of additives to help improve fuel system output, makes it’s far easier to pass routine emissions testing. And by doing so, adhering to the standards and systems in place can help improve the own/operator and the Fleet owner’s bottom line.

Caleb Matzke of Matzke Diesel says:

“We use the Hot Shot’s Secret fuel treatments in our daily service regiments. We also have several customers using the EDT.

We just had -32 degree temps a couple weeks ago and tested the winter treatment in quite a few customer vehicles that were gelling up, and we saw great results keeping those vehicles on the road. We had a variety of customers using competitive oils that were clogging up and too thick and heavy in the cold. They were having issues with their intake valve actuator systems so we also added the HSS FR3 as a reduction in oil operating temperature allowing an easier dry start.

I’m now running FR3 in all of my own diesels, from our 12-weld square body up to our L5p Duramax.”