Diagnostic: Black smoke on Mercedes-Benz - Causes and costs

Black smoke from the exhaust of a Mercedes-Benz (A-Class, C-Class, E-Class, GLA, GLC) usually indicates over-fuelling (too much fuel relative to air) or a combustion problem. Depending on the engine (petrol or diesel), causes and costs differ.

Mercedes diesel (OM654, OM608)

On OM654 and OM608 engines, black smoke is often linked to a blocked particulate filter (DPF) or a faulty injector. A saturated DPF can cause black smoke under acceleration. A leaking or misadjusted injector also produces black smoke. Other possible causes: turbo, lambda sensor, clogged EGR valve.

Mercedes petrol (M264, M282)

On M264 and M282 (turbo petrol), black smoke can come from a turbo leak (oil), a faulty MAF sensor or an injection system that is poorly adjusted. Prolonged over-fuelling can damage the catalyst.

Indicative costs

• DPF clean / regeneration: about €80–200. DPF replacement: €900–2,000 and more.
• Diesel injector: about €350–700 per injector. Turbo: €1,000–2,500 depending on engine.

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