Audi A3: 2.0 TFSI Direct Injection Intake Valve Carbon Buildup

A direct-injection engine sprays fuel straight into the cylinder, so no petrol ever washes over the back of the intake valves. Oil vapour from the crankcase breather bakes onto them instead, and over tens of thousands of kilometres the deposits choke airflow. The car does not break, it just gets progressively duller, rougher at idle and thirstier, and because it happens so slowly the owner adapts without noticing. The fix is a walnut-blast clean, which is a known service item rather than a fault — but it is a real cost to budget on a car that has never had it.

• Rough or lumpy idle, especially from cold
• Gradual loss of low-end response and rising fuel use
• Misfire codes on one or more cylinders
• Hesitation just off idle in traffic

Ask whether the intake valves have ever been cleaned and at what mileage. On a car past roughly 80,000 km with no record, assume it is due. A borescope through the intake is the definitive check if the seller will allow it.

Parts involved: PCV / oil separator.

$600 to $1,600 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Have the intake valves ever been walnut blasted or cleaned?”
• “Does it idle roughly when cold?”
• “Has fuel economy changed over the time you have owned it?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.