We’ve all heard about the infamous smog check and many of us have experienced them.
This article will explain why we need them, how we benefit from them, and what the smog check entails.
To explain why we need smog checks, let’s first discuss how the internal combustion engine (ICE) works.
The engine in your car has several cylinders (anywhere from 3 cylinders to 10 cylinders) that are responsible for making the power that pushes you down the road. Each cylinder takes in a small amount of fuel, it mixes that with a precise amount of air and makes it burn. That controlled burn is what pushes your wheels down the road.
A quick, one-minute video explaining how the cylinders work in your vehicle.
When the engine is running, it creates three by-products that California is concerned about: Hydrocarbons, nitrogen oxides, and carbon monoxide.
- Hydrocarbons are bad because this chemical family combines with NOx to form visible smog.
- Nitrogen oxides (an entire family of chemicals) are bad because they cause “smog” which is that reddish-brown blanket sitting on top of crowded cities. Sunlight plays a large role in this so hot, sunny days will make smog much worse.
- Carbon monoxide is bad because it is a toxic gas. It interferes with your body’s ability to carry oxygen (kind of important!).
In addition to being good for the environment, smog checks can uncover potential problems with your vehicle that make it run less efficiently. This results in lower mileage and increased wear and tear on other components. Wasting fuel due to an improperly functioning engine is wasting money.
It is advisable (but not required) to keep your vehicle well maintained to ensure your vehicle is running as well as it can.
The overall goal of smog checks is to make sure all emissions pieces are installed/functional, and your vehicle is working properly. Let’s go over the process…
NOTE: If your vehicle “check engine light” is on, you must have a mechanic service your vehicle and wait the required amount of time as discussed below.
Before you show up, make sure your vehicle is completely warmed up. Run and drive your vehicle for at least ten minutes. Why? A warm vehicle is an efficient vehicle. You’d be surprised at how hot your engine is programmed to run under normal conditions. This also ensures that your catalytic converter is running at the optimal temperature since it causes chemical reactions that only occur at high temps.
In addition to being more efficient, your vehicle has two modes: open loop and closed loop. Closed-loop is the mode your vehicle uses to monitor all the sensors and operate at peak efficiency. When you start up a cold engine, it runs in open-loop mode. It emits more pollutants from the tailpipe.
A clear sign of a cold engine is the infamous faint white “smoke” that comes out the back of your vehicle when you first turn it on. This is usually just harmless water vapor but it’s a guarantee that you won’t be passing your smog check.
The computer in a vehicle won’t even allow the test to begin unless fully warmed up.
After showing up at your appointment, the smog technician will enter your information into the computer (bring the DMV renewal if you have one) and determine whether your vehicle is subject o federal or California test guidelines. With a few exceptions, all vehicles in California must comply with CA emission standards
Smog checks are performed in three phases.
Phase 1: the functional test
Phase 2: the tailpipe emissions test (1999 and older)
Phase 3: visual inspection
Phase 1: the functional phase
In this phase, the technician will plug the testing equipment into the computer in your vehicle (via the “OBDII” port under your steering wheel) and look for any stored malfunction codes. This will tell if there are problems with sensors, wiring, or other major components in your vehicle.
If your vehicle recently had a malfunction but was repaired, please note the computer stores a permanent code and even if the code was cleared by another person, this permanent code remains in the computer and takes time to clear itself. This cannot be bypassed! How much time? It requires BOTH 200 miles of driving AND 15 trips, or on/off cycles of the vehicle.
For example, today your check engine light came on and you took it to a mechanic. The component that failed was replaced and the light is no longer on (cleared by the mechanic). If you drove one mile to a smog check facility, the vehicle would fail a smog check. Both 200 miles AND 15 trips are required. No mechanic can clear that.
Phase 2: The tailpipe emissions phase
If your vehicle is model year 2000 or newer, this phase is skipped.
This phase measures the chemicals emitted from your vehicle via the tailpipe. A testing device (calibrated periodically) is inserted into your tailpipe and the vehicle is run in two different ranges:
Idle: your vehicle runs at idle and measurements are taken for 30 seconds to verify your vehicle does not emit excessive pollutants at rest.
2500 RPMs: your vehicle is measured while the engine is running at this speed to verify it is operating correctly while driving down the road.
The four chemicals tested are hydrocarbons, carbon monoxide, carbon dioxide, and oxides of nitrogen. Although four chemicals are tested, the test will only fail for hydrocarbons and carbon monoxide.
Failing the emissions portion can occur for several reasons. It is best to show the failure report to a qualified mechanic for their advice but here are some possible reasons:
Hydrocarbons: Improper ignition timing, defective ignition components, a lean fuel mixture, a defective catalytic converter, defective “air injection” components (if present on your vehicle), or possibly low cylinder compression.
Carbon monoxide: This is caused by a rich fuel mixture. It can be caused by a dirty air filter, faulty oxygen (O2) sensor, faulty “Manifold Absolute Pressure” (MAP) sensor, defective “Throttle Position Sensor” (TPS), or possibly a defective Engine Coolant Temperature (ECT) Sensor.
Phase 3: The visual Inspection phase
The visual inspection is the most time-consuming part of the test. The technician verifies that all required components are still present on your vehicle such as:
The catalytic converter. We have all heard this term, but do you know what it does? It intentionally runs at a very high temperature to cause a chemical reaction with harmful pollutants and turn them into less harmful chemicals like water vapor and carbon dioxide.
This device is always under the vehicle since it is part of your exhaust system, located between the engine and muffler.
The “EVAP” system. During normal operation, your engine creates various chemicals that do not exit the tailpipe. Without the EVAP system, those chemicals would vent into the atmosphere and cause both harmful pollution and chemical reactions that cause global warming.
While you drive, the computer in your vehicle periodically tells the system to get rid of the gases that it collects and forces them into the combustion chamber where they are burned and sent out the tailpipe harmlessly.
This system is often (but not always) located under the vehicle.
The gas cap/filler neck. This is inspected to verify it is not leaking fuel.
The PCV valve. This device is in the engine compartment and takes the vapors from the crankcase and routes them into the combustion chamber where the gases are burned.
The EGR valve. This device reroutes a portion of your exhaust back into the engine. This causes lower operating temperature and helps lower the nitrogen oxides (NOX) emitted from your vehicle.
The air injection pump. This device injects air into your exhaust. This can cause continued combustion and reduce the chemicals emitted from your exhaust.
Your vehicle may not have all the components listed above but if they are present, it is verified that they have not been tampered with.
How long does it take?
Smog checks typically take 30 minutes. This can take longer if the components under the vehicle are more difficult to examine or if your vehicle has more emissions components to verify.
How much does it cost?
Smog checks are always separated into two costs: the smog check itself and the certificate. If your vehicle fails the smog check, you only pay for that portion. Our policy is that you are allowed a second test for free within 60 days of the first test. When your vehicle passes the test, you pay for the certificate.
After passing the test, you will be given a paper inspection report and the results are sent electronically to the DMV. This process takes less than 48 hours. You can also take the paper inspection report to the DMV immediately after the test if you need something right away.
If Dennis Automotive can assist you with your smog check needs, call us today!
Enhanced Testing Area
Smog checks performed in an enhanced testing area (an area identified as a high population area) will be performed on a dynamometer. This is a device built into the floor with rollers. Your vehicle tires sit on the rollers and the vehicle is put in gear and the testing is performed under an actual load for more accurate results. In an enhanced area you can also fail for excessive NOx emissions.
Dennis Automotive is not in an enhanced testing area.
The importance of vehicle maintenance
Not only will routine vehicle maintenance help pass smog checks but it also saves you money, increases comfort, and makes your vehicle safer to drive.
The common air filter can cause a rich mixture which causes failures on many smog checks and will reduce engine efficiency and reduce your mileage.
A typical tune-up will replace spark plugs (and possibly other components as well) and ensure that your vehicle completely burns the fuel. Wasted (unburned) fuel will cause high tailpipe emissions and waste precious fuel. You are sure to feel this at the pump.
Keeping your tires inflated to the proper air pressure has many benefits: The tires will last longer, you’ll get better mileage from less rolling resistance, and your braking performance will be better by making sure your tires make contact with the road optimally.
Your mechanic will inspect your exhaust system for leaks. This will not only make your vehicle quieter and more pleasurable to drive, but it will also prevent failure during a smog check. Leaking exhaust can cause failure since not all gases can be tested at the tailpipe.
During routine maintenance, your mechanic will check the condition of shocks and struts. Many people think these are just for comfort but when these items are extremely worn, the ride becomes very soft, so they aren’t noticed. What is happening is that your tires are not maintaining contact with the road. They are “hopping” off the road and that is very dangerous. You cannot steer or brake effectively when this is happening.