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Black Smoke From The Exhaust

Black smoke means too much fuel or too little air: common causes are a clogged air filter, faulty injectors, air flow sensor faults or turbo problems.

Normal risk

Usually drivable, but have it checked. Black smoke raises fuel use and can clog the particulate filter.

Short answer · Why is my car blowing black smoke?

Black smoke is soot from fuel that did not burn completely. On diesels a puff under hard acceleration can be normal on older engines, but constant black smoke points to a clogged air filter, leaking injectors, a boost leak or a faulty air flow sensor. On petrol engines it means a very rich mixture.

On this page

Safe checks you can do

  1. Check the air filterA very dirty filter restricts air.
  2. Read fault codesAir flow, boost or rich mixture codes help.
  3. Note when it smokesOnly under full load, or all the time.

Questions that narrow it down

  1. Is it a diesel or petrol engine?Black smoke is more common on diesels.
  2. Is power reduced?Boost leak or turbo problem.
  3. Is fuel consumption higher?Rich mixture or leaking injectors.

Possible causes

Listed without ranking. Use the questions above to see which ones fit your car.

  1. Clogged air filterNot enough air.
  2. Leaking or worn injectorsToo much fuel.
  3. Boost leak or turbo faultNot enough air under load.
  4. Faulty air flow sensorWrong fuel calculation.
  5. EGR valve stuck openLess fresh air.

Questions about Black Smoke From The Exhaust

Will black smoke damage the particulate filter?

Extra soot fills the filter faster and causes more regenerations.

Is a puff of black smoke on a diesel normal?

A short puff under hard acceleration can be on older diesels; modern diesels with particulate filters should show almost none.