How to Help Your Car Pass Emissions

Passing emissions testing is something that many cars must do in order to continue to be registered to drive. Very new cars are often exempt, but older cars must be registered every year or every other year. If a car fails emissions testing, it must be repaired or adjusted in such a way that it passes, usually within a certain limited amount of time.

A car may fail emissions for a variety of reasons. Some of the most basic reasons might be a leak in a seal between the parts of the engine that contain oil and those that contain fuel, meaning that oil is burned. In this case, nothing special you do on emissions testing day will make the vehicle pass – the faulty part must simply be repaired.

But, some conditions that might make a car fail emissions testing are not constant problems. That is, cars do not produce the same level of pollutants at all times. Most vehicles run most efficiently when the engine is at a particular speed and temperature. Efficiency, and therefore emission of pollutants, will rise and drop several times over the course of any medium-length trip. For best results at the emission station, make sure the car is near a peak of efficiency.

First of all, don’t take a car in to the emission station if it is obviously having problems. A rough idle or other indicator of trouble should be checked beforehand. Emissions testing is able to find problems that are not noticeable to the untrained eye and ear, so obvious problems would almost surely mean a waste of time and money getting the car tested.

Along those lines, make sure the ‘’check engine” light is off. A lit “check engine” light is a result of an error code in the car’s computer. Even if the car is running perfectly, it won’t pass if there is an error code. Often the code will be triggered because of an oxygen sensor not working properly. In such a case, replacing the sensor will not automatically reset the code. Perhaps the “check engine” light will cease to be lit, but the error code might take a few miles of driving to reset. If you’re wondering if the code has been reset after failing the test and subsequently repairing the vehicle, many auto part stores or collision repair shops offer a code checking as a free service.

Take the car in for emissions with the tires properly inflated. Improperly inflated tires may increase strain on the engine, which in turn may cause it to emit more pollutants. This is problematic at test time, since many cars must be driven in place (on a dynamometer) to measure emissions while at speed.

Change your oil before getting your emissions checked, if it’s been more than 4000 miles. Keeping a car regularly maintained, including changing the oil, is a good way to reduce wear and emissions. A car whose oil has not been changed recently or regularly will produce more pollutants than one that has.

Finally, drive the car a bit before taking it in to get checked. A cold engine works a little harder than a warm one, since hot oil is thinner. Other things such as the catalytic converter also work better after the car has been running for a while.