Why did my oxygen sensor fail the smog test?
Failure to pass smog. According to the EPA (Environmental Protection Agency) and CARP (California Air Resource Board) 50 to 60% of all smog test / emission test related failures are attributed to defective oxygen sensors, causing either low or high CO emissions.
Why was my NOx too high on the smog test?
The only emission that was above the limit during the smog test was NO, however both HC and CO measurements were about halfway between “average” and maximum. A 2nd website said, “High NOX emissions are almost always due to a defective EGR valve (or some component that controls the operation of the EGR valve).
Can a car pass a smog test for free?
If you know a smog test service that offers a free pre-test to determine whether or not your vehicle will pass then, by all means, you should use such service before actually having the test done.
What to do if your smog test is too high?
1. Check for fuel control by watching O2 sensor operation. 2. Check the EGR system for proper operation. 3. Perform a catalytic converter efficiency test. 4. Repair as required. I’m a CA Smog Tech, so post or PM me if you need additional help or direction. Sounds like you just repeated what Mike said.
What does high HC mean on a car emissions test?
A high HC reading means the test found high HC (hydrocarbons) in your emissions. In other words, too much gas is left in the exhaust after combustion. High HC can be caused by improper combustion, where:
What to do if your car fails the HC test?
Check cracks in the air duct from the air filter box to the throttle body. If you can’t find any, spray carburetor cleaner around the intake manifold while watching the O2 sensor readings on your scan tool. In many cases you can see the vacuum leak as it sucks in the liquid spray.
What can be done about high NOx in smog?
The solution to this problem is called De-Carbonizing. It usually costs around two labor hours at a smog check repair station. It will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx. 5. Engine Overheating – Inadequate engine cooling can will high NOx.
What to do if your car fails the O2 test?
Look for cracked or unplugged vacuum lines. Check cracks in the air duct from the air filter box to the throttle body. If you can’t find any, spray carburetor cleaner around the intake manifold while watching the O2 sensor readings on your scan tool.