2014 Vauxhall Mokka 1.7 CDTi with a blanked EGR and an engine knock

This 2014 Vauxhall Mokka 1.7 CDTi SE 4x4 had a lot going for it: original paint on every panel, a genuine mileage and a clean cold start. Under acceleration, though, the engine made a small knocking noise, and the engine computer had stored a fuel system overpressure fault. Two emissions and boost systems had also been deliberately altered from the way the factory built them.

The car

The Mokka has the A17DTS 1,686 cc turbodiesel (130 bhp), a six-speed manual gearbox and four-wheel drive. It was first registered in the UK in 2014 and imported to Ireland in 2018, and has had four owners in total. The odometer read 150,048 miles (241,427 km), and the history checks confirmed it as genuine, with no finance owing and no write-off. The service book was present but only one key was supplied.

What we found

Engine knock and a fuel pressure fault

The scan found code P000F, fuel system overpressure, in the engine computer. It means the common rail saw higher fuel pressure than the engine asked for, and is commonly associated with the pressure regulating valve, a sticking regulator or a faulty pressure sensor. On this engine, rail pressure is one of the things that governs diesel knock, so the code and the noise point at the same area. That does not prove they are the same problem: an injector, the dual mass flywheel or something internal remain possible. A fuel rail pressure test and an injector leak-off test are needed to settle it.

Emissions and boost control altered

• The EGR cooler had been physically blanked off.
• A metal rivet had been inserted into the vacuum hose feeding the turbo wastegate, which stops the boost control working as designed.
• The particulate filter read zero pressure difference while reporting that a regeneration was required. That is consistent with a sensor or hose fault, or a filter that has been removed. A delete is suspected, not confirmed.

No fault code related to the EGR or the particulate filter was stored. Factory software would normally record a fault when a system it controls stops responding, so this is consistent with the engine software having been altered. The software was not read, so a remap is not confirmed. Emissions equipment that has been removed or disabled can cause an NCT failure, and modifications of this kind generally need to be declared to an insurer.

Oil leaks

Oil was leaking from several points, including the sump, the injector seals and the pulley side of the engine. The rear of the engine was wet across a wide area, so a leak at the joint between the engine and gearbox is possible but not confirmed. A seal there means taking the gearbox out.

Other findings

• Front tyres at 2.05 mm and 2.53 mm, close to the 1.6 mm legal limit, and the car pulls to the left.
• The air conditioning blows but does not cool, with no fault code in the climate computer.
• The timing belt is marked on the engine as replaced at 128,649 miles, but there is no invoice to confirm the date or what was included.

What it would cost

The immediate work, including tyres, alignment, the fuel pressure tests, injector seals, the air conditioning and an oil leak trace, comes to €1,130 to €2,120. If every contingent item is confirmed, such as a fuel pressure regulator, an engine to gearbox seal, restored EGR and boost control, and a replacement particulate filter, the total could reach €3,430 to €7,820.

Our verdict

Fail, do not purchase in current condition. Any one of the three main issues would be manageable on its own. Together they mean the true cost of putting the car right cannot be established from a pre-purchase inspection, and it could exceed what the car is worth.

The good points were real. Every panel had original paint and every piece of glass was original. 12 of the 14 computers returned no faults, including the airbags, brakes, power steering and four-wheel drive. The brakes had plenty of life, the suspension was tight with no leaking dampers, the interior was in very good condition, and the gearbox and clutch felt normal on the road.

Buying a used Mokka in Ireland: what to check

• Look at the EGR system, the turbo vacuum lines and the particulate filter readings. EGR clogging and particulate filter problems are known issues on this generation.
• Check for oil around the joint between the engine and gearbox. Leaks there are a known weak point and can be expensive to reach.
• Feel for clutch slip and listen for flywheel rattle. Clutch and dual mass flywheel wear are recurring issues on the 1.7 CDTi.
• Ask for proof of the last timing belt change. This engine uses a belt, and a belt failure causes serious internal damage.
• Test that the air conditioning actually cools. Refrigerant loss is a common complaint on this model.

A car can look and drive well and still carry costs that only a fault scan and a look underneath will reveal.