Quote:
Originally Posted by ian.stone
I took the sensor out, it was covered in carbon. Where does that come from, the exhaust, the only route I know is via the EGR valve which must be opening when the engine is cold.
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The sensor on the manifold does get covered in oily, carbony crud very quickly (I think it's actually a boost pressure sensor, but I'm not 100% certain on this).
It gets covered in the crud because a) there's always a few drops of residual oil in the inlet pipework & intercooler, it comes from the turbochargers' oil seals, and b) the exhaust gas for recycling via the EGR is tapped from the exhaust manifold before the DPF, so it's quite sooty. The combination makes the horrible black gunk you see on the sensor.
On my 2014 D4 I used to remove the sensor every 6 months, spray it with carb cleaner and carefully remove the crud with a soft plastic interdental brush.