Nissan Navara YD25 Blowing Black Smoke

Navara D40’s in particular are known for blowing black smoke. This situation with the fuel system itself is due to the fact they have a large nozzle and therefore makes them susceptible to over fueling, especially once wear sets in or if you have rail pressure issues. Any time you have a diesel blowing smoke, ultimately it means the air to fuel ratio is rich or incorrect

It’s advantageous to have a look first at the air side of things, because the D40s can have an intake manifold carbon build-up problem, similar to Tritons. however not as bad, but fairly close and they also are susceptible to an EGR fault. The EGR valve will fail and leak exhaust gas into the intake manifold, therefore further suffocating the combustion process. It is also worth checking the boost levels from the turbo, these YD25’s have a boost control solenoid which can cause the turbo to cease making boost. Generally speaking, it can still be the fuel system, be it rail pressure, or (particularly after about 150,000 km) the nozzle wear is such that you will get a black smoke issue. This is because they run a fairly rich tune from the factory.

Before spending significant amounts of money on the fuel system side of things, it always pays to make sure the intake manifold is clean, that the EGR is correct and closing and opening as should be, and that the engine is breathing effectively and making good boost. Black smoke is always due to it being rich, but it will pay to make sure that is due to fuelling, and not a restriction in air before giving us some of your hard-earned.

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