Hello,
I have mazda 3 2014 , about 100,000 km.
The emission test showed high HC levels while the lambda and other parameters are fine.
It seems that the vehicle consumes a lot of gas.

Here are the readings of the emission test:
CO 0.0
HC 234
CO2 14.8
O2 0.31
Lambda 1.005

Is anybody have a clue what may be the problem?
Thanks!

 

https://www.smogtips.com/failed-high-hydrocarbons-HC.cfm

http://education.seattlepi.com/causes-high-hydrocarbon-reading-during-smog-check-4653.html

Some possibilities that may cause high HC in exhaust:
1. Defective ignition components (such as spark plugs or ignition wires)
2. Improper air/fuel mixture (may be caused by defective oxygen sensor or leaking fuel injectors)
3. Defective catalytic converter
4. Low cylinder compression
5. Evaporative emission control problems

 

Thanks for the answer!
The cylinder compression was also checked and it is fine.
Can a leak in the pipes of the exhast system can lead to that? what is the "vacuum leaks" that are stated in the article?

 

In older engines, vacuum hoses may be part of the control system for certain engine control functions. I doubt a vacuum leak is the source of your problem in this case.

If the leak in the exhaust system occurs after the catalytic converter, this leak should not result in a high HC reading. Where and how is the HC being measured?

Are you getting a check engine light? If so, have the related codes checked.

 

The hc is being checked by a stick that is inserted into the exhaust.
The check engine light is off.

 

Your catalytic converter may be starting to fail. Failing an emissions test and reduced fuel economy are two of the symptoms associated with a bad catalytic converter. A bad ignition system (fouled, poorly gapped or damaged spark plugs and/or defective ignition wires) might also produce these symptoms and could put an additional load on the catalytic converter that may contribute to early failure.

 

Your catalytic converter may be starting to fail. Failing an emissions test and reduced fuel economy are two of the symptoms associated with a bad catalytic converter. A bad ignition system (fouled, poorly gapped or damaged spark plugs, defective ignition wires) might also produce these symptoms and could put an additional load on the catalytic converter that may contribute to early failure.

If it were my car and the plugs and ignition wires have not been changed in the last couple years, I would start with these.

 

I hope you got this fixed, but if the standard methods above don't work, here is something to try. (100K km is WAY too early for a catalytic converter to fail).
1. plugs, wires, etc. Have someone verify that all cylinders and plug connections are good. Especially if the gas mileage is bad.
2. Change the FRONT O2 sensor. Don't check it, don't mess with it, just change it. A "slow" or poorly fouled sensor may not throw a check engine but could be the source of the problem.
3. Check your gas mileage after 1 and 2 are done. If improved, then you can take the test again, If you are close but not there yet, try this old trick:
4. Put a bottle of Iso-heat into the gas tank. (the ISO bottle not the regular heet, red not yellow) Iso-heat is a alcohol-based additive that will cause the exhaust temperature to become a bit higher and will help your cat light-off better. It will not hurt your car. (do not use Isopropyl alchhol straight from walmart! Its mostly water, use ONLY Iso-heet)
5. Just before the emission test drive the car on the freeway or in a method to get the engine and exhaust really hot. This will maximize the efficiency of the cat.


You may pass the HC test but depending on how hot you get it, it may fail the NOX test (if applicable) if it does then just come back after the iso-heat is gone from the tank (next fill-up) and check again.


Either way, these things are easy to do. Good luck.

 

RGAZ, you have made a number of constructive suggestions, but I would not totally rule out a catalytic converter problem. While it is rare for a catalytic converter to fail in 100K km, it does happen. The link below references a 2013 Toyota in the US that had a catalytic converter fail in 60,000 miles.

https://www.yourmechanic.com/questio...d-by-anthony-o

Bad fuel or an ignition problem may contribute to early catalytic converter failure. The OP apparently lives in Israel. Contaminants in the fuel may be more of an issue there than in the US.

 

Thank a lot very helpful!
​​​​​​I was in the garage last week and they cleaned the injection system - it reduced the Hc to 6.
I hope that this problem will not arise again, if yes surelly will take your advice!