How to Pass Smog With an Engine Swap in Colorado

Smog tests are done to guarantee air quality across the country.

Emissions tests, or smog tests, are conducted by companies for the Department of Motor Vehicles. By testing the emissions, or the pollutants released by motor vehicles, the government can determine if a car meets minimum environmental standards. In Colorado, the minimum environmental standards depend on what county you live and work in. If you live or work in Boulder, Denver, Jefferson, Broomfield, Douglas, Adams or Arapaho county, your car must pass an enhanced smog test. Some places in Weld, Larimer and El Paso counties require basic testing.

Instructions

1. Turn your car on. Look to see if there is a lot of smoke coming out of your tail pipe. It is normal for your car to have a little steam coming out of the tail pipe on cold days but not to have a cloud of smoke coming out when you start or drive it.

2. Crawl under your car and locate the exhaust pipe. Look along the pipe to see if there are any cracks or holes. Having an exhaust leak will make it harder for your vehicle to pass emissions tests.

3. Look for a catalytic converter along your exhaust pipe. The converter helps reduce the pollutants that are released from your vehicle by burning any of the air-fuel mixture that may have been released from the engine into the exhaust system. Having a catalytic converter is a requirement of both the basic and enhanced tests in Colorado.

4. Ensure that your replacement engine has all emissions equipment that came on it originally. If you used a crate engine, it came from the factory with emissions equipment attached to it. Checking for emissions equipment is especially important if you bought the engine used or from a private party because the emissions equipment could have been removed before your purchase.

5. Take your car to a shop that can tune it. If you put an engine in a vehicle that is not stock, the engine might not be tuned properly. If your car is using too much gas or oil, a tune can correct it. If your vehicle is using too much oil or gas, it will be harder for your car to pass an emissions test.

6. Take your car to your mechanic for a tune-up. Keeping your car current on maintenance, such as oil changes, will help it pass emissions.

References

• Colorado Department of Motor Vehicles: Smog & Emission Checks in Colorado
• AA1Car.com: Emissions Testing: Will Your Car Pass?

Resources

• Colorado Department of Revenue: Emissions Information