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Smoke When Accelerating

Smoke that appears under acceleration is usually black on diesels from too much fuel or too little air, and blue-grey from oil burning under load; a clogged air filter, boost leak or worn turbo are common causes.

Normal risk

Have it checked soon. Heavy smoke can damage the DPF or catalytic converter.

Short answer · Why does my car smoke when I accelerate?

Under acceleration, the engine burns the most fuel and needs the most air. If air is short, for example from a dirty filter, a leaking boost pipe or a weak turbo, fuel does not burn fully and black smoke appears. Blue-grey smoke under load means oil is getting into the cylinders or the turbo. The colour is the main clue.

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Safe checks you can do

  1. Note the colourBlack: fuel or air; blue-grey: oil.
  2. Check the air filterA clogged filter starves the engine of air.
  3. Listen for hissing under boostA hiss points to a boost leak.

Questions that narrow it down

  1. Is the car a diesel?Black smoke is more common on diesels.
  2. Is there a power loss?A boost leak or turbo fault is likely.
  3. Is oil level dropping?Oil burning is likely.

Possible causes

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

  1. Clogged air filterToo little air.
  2. Boost leakTurbo air escapes.
  3. Faulty EGR valveToo much exhaust gas recirculated.
  4. Worn turboOil or low boost.
  5. Faulty injector or MAF sensorWrong fuel quantity.

Questions about Smoke When Accelerating

Is black smoke normal on diesels?

Modern diesels with a DPF should not smoke visibly. A puff on hard acceleration on older diesels was common.

Can smoke damage the DPF?

Yes. Excess soot fills the filter quickly.