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Thread: 3.9 V8 Popping and Rattling under load

  1. #1
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    3.9 V8 Popping and Rattling under load

    Hi

    The rangie has had a issue which im chasing. Putting it into shop i a week or so but would like to figure it out.

    Symptom is when under load such as going up a slight hill sitting around 3000 it starts popping not really back firing more just popping. Then if you drop it down a gear it starts making a rattling noise like a loose exhaust and no real power just noise. once over the hill it runs rough for a while and then is ok again after a while.

    I have changed leads to see if that helps but didn't checked plugs which were black but didn't change after a clean. Next i was going to change coil

    Any help or pointers would be great.

    Cheers

  2. #2
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    Sounds like it is pinging - check your timing. Likewise while a 3.9 should run OK on 91 Ron fuel - try it on 95 or 98 Octane and see if the issue continues.
    REMLR 243

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  3. #3
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    Sounds like sticking exhaust valves to me.
    quite common on 3.9.
    regards Philip A

  4. #4
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    Quote Originally Posted by garrycol View Post
    Sounds like it is pinging - check your timing. Likewise while a 3.9 should run OK on 91 Ron fuel - try it on 95 or 98 Octane and see if the issue continues.
    Will check today. After driving to work it seems to be getting worse. Any real input with right foot and it gets upset. Always run on 95ron

  5. #5
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    Under load, sounds more like the ignition module than sticking valves to me, but sticking valves also give the same kind symptom of sudden misfire type power loss. worse if it's the exhaust valve.

    Do you have excessive oil consumption? excessive tailpipe emissions?
    Do you have a filthy carbon-sludged valvetrain?
    What is the state of your oil? (lifters blocked?)
    Is your static timing set correctly?
    Is the power loss sudden or surging or is it just waning and dying?

    Do you have excessive valvetrain noise on cold startup in the morning, or does it get noisier with a hot engine?
    Roads?.. Where we're going, we don't need roads...
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  6. #6
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    How many K's has this engine done?, It sounds like the valves or lifters are playing up on you.
    I had the lifters replaced on my 4l V8 at about 250K and it made quite a difference
    You only get one shot at life, Aim well

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  7. #7
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    Checking timing today. 260000 on engine. I have spare dizzy one has a scorcher amp but not sure how old. Will try another coul and check all connections and look at replacing amp.

  8. #8
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    Just checked timming and was way over the markings. Brang it back to 10btdc. Test drove and still a bit rough and popping up hills but no rattling/pinging. Will check modukes and connections tomorrow

  9. #9
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    Also seems to struggle between 2000-3000 rpm get rough and feels like its missing. Feel vibration in cab

  10. #10
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    Bring it back to the standard 3 BTDC and see how you go - if OK then advance until issues start again then back off until OK.

    Your 3.9 should be Ok on 91 Ron at 9BTDC
    REMLR 243

    2007 Range Rover Sport TDV6
    1977 FC 101
    1976 Jaguar XJ12C
    1973 Haflinger AP700
    1971 Jaguar V12 E-Type Series 3 Roadster
    1957 Series 1 88"
    1957 Series 1 88" Station Wagon

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