Car · Problems

Black smoke when accelerating

Black smoke is unburnt fuel: too much diesel for the available air. It is common on diesels driven mostly in town.

UrgencyLow
Can I drive?Yes, carefully
Likely causesClogged EGR valve

Likely causes

  1. Clogged EGR valve30%
    Garage price: EGR valve £275 – £740
  2. Dirty mass air flow sensor25%
    Garage price: Mass air flow sensor £90 – £255
  3. Dirty or faulty injector25%
    Garage price: Diesel injector £245 – £650
  4. Split turbo hose20%

What you can check yourself

  1. Check the air filter: a clogged one alone can cause black smoke.

Fault codes often linked

P0299 Turbocharger underboostP0400 Exhaust gas recirculation flowP0401 EGR flow insufficientP0402 EGR flow excessiveP0403 EGR control circuitP0404 EGR control circuit range or performanceP0068 MAP/MAF and throttle position correlationP0100 Mass air flow sensor circuit

Frequently asked questions

Black smoke when accelerating: what causes it?

Likely causes: clogged egr valve (30%), dirty mass air flow sensor (25%), dirty or faulty injector (25%).

Can I drive?

Yes, carefully. Urgency: low.

Indicative estimate. MecaScan cannot see your vehicle: always have a diagnosis confirmed by a professional, and never work on brakes, steering or airbags without the skills.