M9R Boost / EGR problem

Discussion in 'Mechanical - Engine, Gearbox, Exhaust etc' started by planb2010, Mar 13, 2019.

  1. Hi guys,

    I hope you don't mind me posting here as i don't have a megane but an X-trail with the same engine so am hoping that the knowledge might be the same.

    Engine is M9R 2.0 DCI 173.

    It was remapped but had an EGR fault, EGR was replaced but didn't realise it needs position learning so left it. The DPF failed so i replaced the full exhaust and whilst having the ECU reset for the DPF i asked them to relearn the EGR but the fault persists with P0409.

    I was going to get the EGR mapped out (it's blanked off now) but the remapper wanted the car stock and so hopefully that's been done but what i also noticed is another problem and am not sure if it's map or could be EGR having an effect.

    Mostly noticed under full throttle, the turbo just drops out from full pressure 22psi to between 8 and 14psi then slowly builds back up not the normal spool up and not very fast for the RPM so definitely being controlled by the ECU. This is just what i want to know really is if a fault with the EGR is present would the ECU respond by dropping the turbo pressure through the RPM and by remapping and also egr delete work.

    I've currently got it booked in to Nissan for them to do a software update on the ECU to make sure the ECU is running the default map and not any settings left over by the old map.

    I've also replaced the turbo, maf, map, boost solenoid and as said EGR, so these should be all good.

    If anyone can shine any light i'd appreciate it as currently the x-trail forums are not allowing signups so couldn't ask there.
  2. I was told that you can't delete or block off the EGR valve, as its needed for the ecu and fuel trimming.

    I run a Grand Espace with the same engine, my was mapped due to a DPF delete been running it for 6+ years now with no problem, its now on 170k miles and gets hammered every day :laughing::laughing: great engines
    Gavin. likes this.
  3. The turbo is a variable vane unit, if its not backing off or the vanes are sticking it will then over boost, ecu is shutting the fuel back to save the engine from blowing.

    You might even just have an air leak in the pipework the the actuator allowing it to over boost.
  4. Thanks for the replies.
    I used a vacuum test pump to check the pipes and the actuator, all seems to respond fine, the actuator moves slowly and freely as per the vac range 5 to 17 hg or what ever it was!
    I thought it might be a vac leak but according to my reading up, the turbo actuator needs full vac for the vanes to be in full boost position, less vac means less boost.
    Interesting, i've read that it is possible to blank it off, funny that we hear all different stories!
  5. Mine eats the egr pipes, think i have had 3 and it needs another one now, thats why i asked about deleting it.
  6. I can't see why you can't remove it, i've read it on x-trail forums that plenty have.
  7. Not going to touch mine as it won't be worth it, cars worth too much to me working :laughing::laughing:
  8. tof73

    tof73 RSM Club Member

    EGR can be deleted totaly, there is 2 guys on here that knows quite a bit on here (Vioar & Bulardas) is there forum name, they can advise whats required to do so.
  9. CJ_RSport

    CJ_RSport RSM Moderator

    When you say the turbo just drops out does it build back up to full boost higher in the revs?

    Id be checking vac lines for leaks and kinks,

    EGR can be mapped out and blanked, if blanked it needs a blank with room for the disc to move on startup and shutdown as even though its mapped out it still needs to configure position. or some just weld the pipe an inch away from the egr.

    very rare but vac pump can fail. im sure full vac is around 25 on the vac gauge so if only reaching 17 you could have a vac leak

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