Diagnostic: Black smoke on Audi - Causes and costs

Black smoke from the exhaust of an Audi (A3, A4, A6, Q3, Q5) usually indicates over-fuelling (too much fuel relative to air) or a combustion problem. Depending on the engine (TFSI or TDI), causes and costs differ.

Audi diesel (TDI)

On TDI 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.

Audi petrol (TFSI)

On TFSI (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 and DPF (if fitted).

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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