Diagnostic: Black smoke on Volkswagen - Causes and Prices

Black smoke from the exhaust of a Volkswagen (Golf, Polo, Passat, Tiguan, T-Roc) usually indicates excess fuel in the combustion or a problem with the exhaust system (DPF, turbo). Depending on whether your vehicle is TDI (diesel) or TSI (turbo petrol), causes and costs differ.

Volkswagen TDI (diesel)

On TDI engines (1.6, 2.0), black smoke is often linked to a blocked diesel particulate filter (DPF) or a faulty injector. The AdBlue system can also be involved (AdBlue injector, dosing or fluid quality). A saturated DPF causes black smoke under acceleration and sometimes the check engine light. An injector that is leaking or out of adjustment enriches the mixture and also produces black smoke.

A clogged EGR valve and the turbo (wastegate, oil leak, geometry) are other possible causes on high-mileage Volkswagen diesels.

Volkswagen TSI (turbo petrol)

On TSI engines (1.0, 1.4, 1.5, 2.0), black smoke can come from the turbo (oil leak on the exhaust side), the MAF sensor or the injection system. Prolonged over-fuelling can damage the catalyst.

What to do

Avoid hard acceleration and long journeys at full load until the cause is identified. A diagnosis by a professional (fault codes, pressure and DPF checks) is recommended.

Order of magnitude of costs

• DPF regeneration / clean: around €90 to €220.
• DPF replacement: around €900 to €2,000 depending on model.
• Diesel injector: around €300 to €600 per injector.
• AdBlue injector: around €220 to €500.
• Turbo: around €1,000 to €2,500 depending on engine.

My Auto Check-up helps you gather the information (engine, mileage, when the smoke appears) to estimate costs before your garage appointment.