Faulty injectors: symptoms and costs

Injectors deliver the right amount of fuel into the engine. When they get clogged or fail, the symptoms are often clear. Here are common signs and costs to expect.

Common symptoms

Misfires at idle or under acceleration, loss of power, engine spluttering. Abnormal smoke from the exhaust (black on diesel = over-fuelling; white = leaking injector). High fuel consumption. Engine warning light on (injection fault stored). Hard starting when cold (especially diesel).

Common causes

Clogging (poor fuel quality, saturated filters). Wear of internal parts (needle, seal). Corrosion or short circuit (injector coil). On diesel, piezo or common rail injectors are sensitive to fuel quality and fuel filter maintenance.

What to do

At the first signs, avoid heavy load and have a diagnostic (fault codes, leak or spray test). Tank cleaning may be enough if clogging is light; otherwise replace one or more injectors.

Order of magnitude for costs

Petrol injector: €150–500 each (depending on vehicle). Diesel injector (common rail): €300–800 each and more. Full set (4 cylinders): €1,200–3,000 and more. Labour: variable depending on access. My Auto Check-up helps you describe symptoms for an initial estimate before visiting the garage.