Renault Trafic: dCi injector failure — rough running, smoke and hard starting

Injector failure is a recognised fault on the dCi engines in this Trafic, showing as rough running, excessive smoke and poor starting. Diesel injectors are precision parts working at very high pressure, and they are punished by contaminated or poor-quality fuel and by a fuel filter left in too long — both of which are more likely on a working van than on a private car. The symptoms come on gradually and owners get used to them, so a van that "always takes a couple of goes in the morning" is describing this without realising. Injectors are usually replaced as a set, which is what makes the bill significant rather than trivial, so it is worth finding before you buy rather than after the first cold week.

• Rough or uneven idle, particularly from cold
• Excessive smoke from the exhaust, grey, black or white
• Hard starting, or needing to crank for several seconds
• Knocking or diesel-rattle that is louder than it should be
• Loss of power, or an engine warning light with fuel-system codes

Get there before it has been started, because cold starting is where this shows. Watch and listen as it fires: it should catch within a second or two and settle into an even idle, not crank repeatedly or stumble for the first half minute. Stand at the back and watch the exhaust as it starts and again as it is revved once warm, noting any heavy smoke and its colour. With the bonnet up at idle, listen for one cylinder sounding harsher than the others and for a diesel smell around the top of the engine, and look for wet fuel or a dark stain collecting around any injector. On the drive, accelerate hard once and note whether it pulls cleanly or hesitates, and watch the dash for a warning light. Ask when the fuel filter was last changed and check it against the service record, and ask whether any injector has ever been replaced — one new injector in a set usually means the rest are the same age. If a workshop inspection is possible: an injector leak-off test identifies which injectors are at fault and is the standard check.

Parts involved: Fuel injector.

$900 to $3,800 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.

• “Does it start easily every morning, first turn of the key?”
• “When was the fuel filter last changed?”
• “Have any injectors ever been replaced?”

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.