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Miss Who? Miss fire... still!

Discussion in 'Range Rover' started by Doo, Jun 21, 2020.

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  1. Doo

    Doo Well-Known Member

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    Most will know George, but for those who dont, 2000 V8 4.0.

    Had misfire for ages and replaced a bunch of stuff before finally figuring out it was the Crank Sensor.

    Anyway, it murdered the cats so I de-catted it until I discovered the cause as above.

    I bought new cats and will fit them soon as my mate has a slot. BUT.... I notice I'm getting a poor throttle response almost to the point it feels as if I'm running out of petrol.

    I hope it's because the car is running without cats so is running rich and when hot it doesn't "like" it o_O

    But to be honest, it feels as if it's the Crank Sensor again even though it's barely covered 200 miles since being fitted!

    Is it possible it's gone faulty already?:rolleyes:
     
  2. RangeRoller dt

    RangeRoller dt Well-Sprung Member

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    She letting you keep it now?
     
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  3. Datatek

    Datatek Well-Known Member

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    Anything is possible, lots of duff components on the market these days.:( More likely the ECU doesn't like the lack of sensor input.
     
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  4. myfirstl322

    myfirstl322 Well-Known Member

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    +1... fit the cats then see.
     
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  5. oakey

    oakey Well-Known Member

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    All the electronic stuff and sensors are designed for Cats. I would refit
     
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  6. oakey

    oakey Well-Known Member

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    Or reset adaptive values?
     
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  7. Mark Piercy

    Mark Piercy Well-Known Member

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    It's quite possible the lack of cats .
    Does your have pré and post lambda sensors?
     
  8. Henry_b

    Henry_b SPARES OR REPAIR

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    Fuel pressure.
     
  9. kermit_rr

    kermit_rr Well-Known Member

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    If it doesn't have post cat sensors then it won't know or care they are missing.
    Anyways, pretty sure the post cat sensors only tell you if the cats are working and don't affect emissions/running
     
  10. Mark Piercy

    Mark Piercy Well-Known Member

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    If it does have the post cat sensors it can cause faults on the ecu side. As it is émission related its a priority system and will cause a code my mate.;)
     
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  11. kermit_rr

    kermit_rr Well-Known Member

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    Agree on the faults, just wasn't aware they affected fuelling in any way
     
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  12. Mark Piercy

    Mark Piercy Well-Known Member

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    The post lambda check the cats output. If the cat/s don't behave the way the ecu predicts it can effect fueling on some systems.
     
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  13. pwood999

    pwood999 Well-Known Member

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    Was the old crank sensor bad output, or actually damaged ? Check the teeth on the flywheel, and make sure none are missing. I believe it should have 58 teeth on the Thor, with two missing at 60deg before TDC.
     
  14. Doo

    Doo Well-Known Member

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    Thanks for all the replies. I was kinda leaning towards "it's because the cats are missing" but wanted a 2nd opinion.

    It never occurred to me to check for missing teeth... But the new CS made a difference when I put it in. Granted it was a cold start, but the spark testers showed the sparks were now back in tune. I messaged my mate, but no reply as of yet so not sure when I'll get the cats on :confused:

    I'm trying to not use the car as I want to sell it and have ordered a heap of new parts. Whole exhaust system, roof lining, new (well, used) wing and bonnet, etc. Someone going to get a decent motor all the same. I have lavished money on it over the 4'yrs I've owned it... Someone else's turn now.
     
  15. Doo

    Doo Well-Known Member

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    Well, finally got it code read by the master and it showed one of the 2 O2 sensors is unhappy.

    Sometimes it's working, but mostly it's not! Seems the last chap who code read it "isn't very good with older cars!" o_O

    Wait! What? An O2 sensor does the same job on a 2 year old car as on a 20 year old car :rolleyes:

    Anyway, ordered a pair and hoping they will be in today around lunchtime.

    The same chap suggested my head gaskets are gone :eek: I pointed out his boss fitted this engine not 22 thousand miles ago and it's been treated very well with a total of 5x oil changes (the original when the engine was dropped in followed by 4 more from me), it's never been allowed to overheat and doesn't get thrashed along motorways or tow heavy trailers. His boss agreed it's unlikely, but there is speak of it still being under warranty so if it "is" knackered, I may be covered...

    However, I'm hoping it's just a dodgy sensor, but am replacing as a pair and will keep the "good" one as a spare for testing purposes.
     
  16. kermit_rr

    kermit_rr Well-Known Member

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    sounds like it could be a dodgy connection, it doesn't take much at all
     
  17. Doo

    Doo Well-Known Member

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    Nah, the connections are excellent. We think it got cooked when the crank sensor cocked up the timing and fried the cat. It was switching properly, then it would drop then come back....
     
  18. Henry_b

    Henry_b SPARES OR REPAIR

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    On live data the sensor should fluctuate between 0-5v if it is a static number the sensor is shagged.
     
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  19. Henry_b

    Henry_b SPARES OR REPAIR

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    Mind you when/if an O2 sensor fails the Thor will go into an open loop Rich mixture, it shouldn't misfire.
     
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  20. Mark Piercy

    Mark Piercy Well-Known Member

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    The first O2 sensor reacts to the engines emmisions.
    if you have a post cat sensor as well, that reacts to the cat holding and releasing oxygène.
    If the post cat doesn't respond or fluctuate, it could be either a dead cat (meaow) or a dead sensor.
    By adding an external fuel via the air intake it will cause the both sensors to react, if they still don't react they are indeed dead... The fuel trims will also react and drop when the gas/fuel is added. :cool:
     
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