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Nissan Navara YD25 Blowing Black Smoke

Why do Navara Blow Black Smoke

635 379 Brooke Hamilton

Why Navara Blow Black Smoke

Its one of the most common questions we get; Why does my navara blow black smoke?

The primary reason for this is that they are very close to the AFR limit of what will blow smoke from the factory, whereas other manufacturers are not. So basically, things don’t have to start going wrong by a lot before it’s a visible issue.

So what can be contributing issues? Lets have a look

What makes my Navara blow black smoke

  • EGR faults.
    1. Probably the most common is the issue where the butterfly fails in the EGR valve. Basically these use a plastic gear set that links the electric motor and the valve itself. They usually don’t throw a fault code as electrically, everything is fine.
  • Injectors:
    1. These injectors flow the most out of any ute in Australia. Nissan engineers decided that higher flow rates and shorter durations were the way to go. It also means however that if something starts to go wrong, it goes really wrong as the higher flow rate exacerbates any errors.
    2. For more information on the injectors, click here
  • SCV faults.
    1. Linked to the injectors above and definitely more common than injectors is the SCV worn out. The SCV basically is the throttle of the fuel pump and therefore any errors in rail pressure result in flow rate errors through the injectors.
    2. A common symptom of failing SCV is stalling on occasion when stopping at lights or pronounced engine rattle when coming back to idle.
    3. There are two types of SCV. SHORT or LONG – both of which are available at good prices by clicking the Short or Long words.
  • Incorrect maf readings due to split hoses.
    1. Split hoses is another favourite of the Navara. Check the video showing how much they expand! These control fulling based on the MAF readings, but if its reading air flow that’s then being lost out a hose, its putting in fuel that it doesn’t have the air for and hence you get smoke.
    2. You can see how much they expand here without any load! it looks horrific on the dyno!
  • Blocked intake manifold.
    1. Common for all new EGR cooled Diesels, the intake manifolds clog up with carbon residue and will restrict the flow. Whilst it can be detected by the MAF where it pulls fuel, usually the build up in the intake chokes #4 and #3 worse, resulting in rick AFRs for these two (meaning Smoke) and lean for #1 + #2.

So there it is. That’s not an exhaustive list of things it can be (and it’s a Navara which is always coming up with creative ways to fail) but it is by far and away the most common.


2 comments
  • Ben R

    Mine, is particularly bad on startup, and ive also had my pathfinder lose power and the slip indicator flash when i planted my foot when taking off from a standing start. (no the tyres didn’t spin) The EGR is blocked and the manifold didn’t look too bad when i did it.

    Thinking that i might start with replacing the scv and also take a look at the glowplugs while i’m at it. Have you guys got any other suggestions to look at while i have my head under the bonnet?

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