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Thread: 2000 XKR running lean!

  1. #1
    Junior Member
    Join Date
    Feb 2015
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    Exclamation 2000 XKR running lean!

    Just replaced 2 upstream O2 sensors (BTW use DENSO, not BOSCH). No codes for 2 months now (knock on wood).


    1. In neutral rev up to 3 K rpm - runs OK - give it a little more, starts misfiring!
    2. Put in gear and drive, I can now can take up to 5.5 K rpm
    3. Monitoring Fuel pressure at rail; 39-40 PSI at idle, 57-58 at WOT. Hose from fuel pressure regulator to Intake manifold is good!
    4. Monitoring A/F ratio using OBDII reader and Torque app - at Idle 13.7- 14.3 AFR, hit the gas, AFR goes to 18-20, Engine knocks, I back off of course.

    5. Cant find any vacuum leaks! Put hose clamp on at air inlet tube/throttle body junction; thought as S/C drew air in harder, more air might be getting past TB seal. Airbox to air tube (just past MAF) also nice and _very_ snug.
    New test drive shows same problem still there!!

    6. Any advice from the hands on tuners or pro mechanics? (Please, if you don't work on engines keep the guesses to yourself - I'm already good at that, Thanks!!)
    7. Where else should I look for vacuum leaks? Oh, I also put some Lucas Injector cleaner lubricant, the thinking being Injector might be stuck closed.
    (8. How often does this really happen ?)


  2. #2
    Senior Member
    Join Date
    Apr 2016
    Near Berlin
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    The best way that I know off to find vacuum leaks is to use the short term fuel trims.

    If you use the OBD connection and have a live feed of the fuel trim Which is shown as a graph. You can spray brake fluid at the joints.When you have the correct place the fuel trim will change. This video explains how to do it at the end of I remember correctly.

    Grumpy Old Git
    “When a government is dependent upon bankers for money, they and not the leaders of the government control the situation, since the hand that gives is above the hand that takes. Money has no motherland; financiers are without patriotism and without decency; their sole object is gain.”
    Napoléon Bonaparte

    2003 (botox) S type 3.0 sport with manual gearbox, as rare as rocking horse apples

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