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2011 Ford Fiesta - Failed emissions

I don’t know why my car failed the smog test

Because your car has a problem. And the emission testing station should have told you what failed. You didn’t tell us so it is very, very hard for us to help you.

If you didn’t drive it very far, you might pass if you take 30 minute drive before a retest - but that’s just a wild donkey guess.

Is your check engine light on? If it is go to an auto parts store and have them read the code. Post the codes here, they will look like P1234, you may have more than one. Did the shop doing the test tell you what failed? They should have told you.

You should have received a print-out of the results of the emission test.

This print-out reflects what part of the emission test the vehicle failed.


I also don’t know why your car failed the smog test.


All the readings indicate a very rich mixture. The most likely causes are:

  1. Oxygen sensor failed
  2. Air leak around inlet manifold
  3. exhaust leak before the oxygen sensor
  4. coolant temp sensor fault
  5. misfire
  6. mass airflow sensor out of range

Where did you get the reading from I don’t see them posted.


How do you know? Are you the original poster under a different name?