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Running Lean -

Discussion in 'Z32 (300ZX)' started by SRRAE, Sep 8, 2009.

  1. SRRAE

    SRRAE Well-Known Forum User

    Using the datascan application and a decent emissions tester (good enough to give an idea of emissions) all saying that one bank of my engine is running lean.

    The drivers side O2 sensor is repoting very low or at time zero, also the CO2 reader that we have is reporting -0.8 while the passenger side is reporting about 3.4 3-6

    What could be causing this?
    I heard the PCV valves can sometimes cause engine to run lean. They are only about 4 years old but its not been used at all in 4 years so may have clogged up.

    Any ideas?
  2. zbloke

    zbloke Well-Known Forum User

    What readings are you getting from the passenger side O2 sensor when its giving you the high CO2?

    What readings do you get from the O2 sensors when you raise the engine speed to approx.1500/2000 rpm, do they switch from rich to lean or do you have one that just sits on zero all the time?

  3. SRRAE

    SRRAE Well-Known Forum User

    this is using the datascan software where the readings are from 0-100.
    At 2000 rpm the drivers side, (Which is the side running lean) the reading wildly fluctuates from 20ish to 80ish like a pendulum, which is what I expect.
    However the side which seems to be running fine, the O2 readings changes but only very minor and not the flipping from rich to lean at least 5 times in 10 seconds like th book says it should.

    Could a faulty O2 sensor on one side of the car cause the opposite side to run lean?
  4. zbloke

    zbloke Well-Known Forum User

    Sounds to me like the passenger side O2 sensor has died, its running rich on that bank because when the ECU stops seeing O2 sensor feedback it defaults to a rich condition for safety reasons.

    You could try swapping the O2 sensors side to side, if the fault follows the sensor it confirms sensor failure, have you tried carefully cleaning the tip of the sensor, checked the wiring to the sensors is all good?
  5. SRRAE

    SRRAE Well-Known Forum User

    Yeah we have tried cleaning the O2 sensors but thats whent his issue occured. The wiring is OK I did check that a few days ago.
    The other side is not actually running rich, if anything the other side is OK, but its not doing the flip between rich and lean like it is mean to at 2000 rpm.
    I plan to swap them over tomorrow and see what happens.
  6. Mr.F

    Mr.F Inactive

    Surely it is the defective LH sensor that is causing that bank to run rich - I'd be more worried about that than a low idle figure for the side where the O2 sensor is obviously working fine...

    Change the defective sensor and the engine will be back in balance, then ensure that mixture is safe under load.
  7. SRRAE

    SRRAE Well-Known Forum User

    Are O2 sensors still £80+?
  8. Mr.F

    Mr.F Inactive

    If you have been transported five years into the past - yes.
    The last one I sold was £101.83 + VAT and may have gone up again since...
  9. SRRAE

    SRRAE Well-Known Forum User

    Ironically that is when I bought 2 new ones and replaced them.
  10. andy

    andy Well-Known Forum User

    Sorry if this loses you any trade Mike but the universal 3 wire sensors from ebay sellers come in at around £15 plus postage and work absolutely perfectly. Fair enough they may not last as long but how many could you buy before you hit £100 plus VAT? ;) All they require is a simple splice into the old sensors flying lead :)

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