Type X 180 - SR20DET Lean under vacuum

Thread in 'Technical Questions' started by 180Dorifto, Jun 27, 2020.

  1. 180Dorifto

    180Dorifto New Member

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    Hey all, forgive if in the wrong area. You're literally my last hope, as I'm out of ideas.

    I'm experiencing massive lean issues when driving. It only occurs when in vacuum-off boost. So, motorway driving, cruising or slight acceleration off-boost.

    I'm observing this on an AEM UEGO thats definitely okay and reading correctly, it'll creep to 20:1 and start breaking up.

    It's an intermittent problem, happens consistently at 4K RPM, but intermittent everywhere else.

    Its a late model 180, non vvt blacktop:

    Standard Turbo
    Standard MAF
    Standard Intake
    Front Mount
    Walbro 255 (with relay)
    EBC normally set to 1 bar (disabled while I'm trying to figure this out)
    New Plugs
    Tested Coils
    New Coolant Temp Sensor
    Timing at 15 degrees at idle
    Short term self leaning reset via Nissan Datascan.

    If anyone can help, I'd massively appreciate it. Maybe even buy you a drink if you're in the midlands ;)

    It's the J4 type ECU, if that aids troubleshooting.

    Help me DriftworksForum-enobi, you're my only hope.
     
  2. r3k1355

    r3k1355 Well-Known Member

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    Changed the fuel filter recently?

    Have you had the injectors cleaned and flow tested?

    Checked fuel pressure?

    How is the FPR vac line hooked up?

    Pulled ECU error codes?
     
  3. 180Dorifto

    180Dorifto New Member

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    Thanks for the reply,

    I've changed the fuel filter during the diagnosis of all this, no change.

    Have NOT had the injectors done yet, purely based on the fact that they work fine at idle and when in positive manifold pressure. This literally only happens in vacuum.

    Fuel pressure checked, regulator replaced just in case.. All okay

    Vac line is T'd off the manifold. Has been like this since I imported with no problems.

    No ECU error codes, all sensors/TPS/MAF reading correctly.

    Might be worth mentioning, this issue appeared out of nowhere and has steadily become worse and worse.
     
  4. Spawn_CA18

    Spawn_CA18 Member

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    I would start from checking the ECT sensor resistance and MAF voltages.

    ECT sensor is known to cause similar issues.

    If them 2 are OK, Fuel pressure regulator would be next to check...
     
  5. r3k1355

    r3k1355 Well-Known Member

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    Having the FPR on a T-piece is not great, should have a direct connection to the vac/pressure source.

    It's probably not your issue tho, but checking/replacing vac lines is a good place to start.
     

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