Skip the auto shop - Our mechanics make house calls

Q: Failed emmissions test

asked by on

I went to get my emissions checked today and my car failed the test. The hydrocarbons read 9.0 pm which was off the chart and the CO% was 361. Do you know if new plugs and wires would bring down the numbers enough to pass the test? Is there anything else I could replace to help pass the test?

A: Hello. If the plugs and wires have not been...

Hello. If the plugs and wires have not been replaced for several thousand miles, then replacing them may indeed help lower emissions levels. New plugs and wires can help produce a stronger spark, which will result in a cleaner burning fuel mixture. However, due to the excessively high hydrocarbon levels, this alone may not be enough for the vehicle to pass the test. A full tune-up, along with a thorough inspection of the ignition and fuel systems, may help lower emissions levels further, perhaps enough for the vehicle to pass. I would also recommend checking the condition of the catalytic converter, as a faulty catalytic converter can cause the vehicle to produce higher emissions as well, particularly CO. If you need help, a certified technician from YourMechanic can replace the catalytic converter for you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Hello, the analysys of exhaust gas of my car show that it contain a lot of unburnt fuel, what is the problem? how can I solve it?

Without knowing the vehicle and engine along with some testing information on the vehicle it is a speculation on my part then you have one or more of the following problems and would need further tests to isolate the problem....

Q: Truck shakes at high speeds

Hi there: To answer your question simply; YES, even slight damage to your sway bar linkage can cause severe shaking above 55 mph. You also indicated that the tire has a little play when you jack it up which might...

Q: The car is not firing. There is oil on the plug number 4

Oil on the spark plugs is never a good sign. if the oil is on the outside of the spark plug, you probably have a leaking valve cover seal. If the oil is on the inside (business side) of the...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.