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Thread: XJR lacking performance

  1. #11
    Senior Member Alec Escolme's Avatar
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    Quote Originally Posted by 2woody View Post
    "Bad" cats don't really exist for these - they're very stable metal-substrate cats
    Did you read the links I posted?
    Super V8, X358 Facelift + Portfolio Vents + Wald Spoiler, Black Cherry with Ivory/Charcoal leather + Black SuedeCloth Headliner, Rear Entertainment, Picnic Trays and Split Rear Reclining Seats. 200 Cell Cats, 2.5 SS Custom X-Pipe Exhaust, JagDroid Headunit, Arden Sportlines with 295 rear
    BMW 650i LCI Facelift, Convertible, Black Saphire with Cream/Black interior
    Ex. XJ X350 3.0 Silver/Dove

  2. #12
    Senior Member Stagnite's Avatar
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    Quote Originally Posted by 2woody View Post
    "Bad" cats don't really exist for these - they're very stable metal-substrate cats
    Bad cats was the problem for this guy. Have a read, its very conclusive.
    Currently enjoying:
    2007 XKR Convert. Frost Blue, Ivory leather. 32k
    2006 S Type R. Slate Grey, Dove Grey leather. Full Burr Walnut upgrade, Rear DVD screens. 64k.
    1999 XKR Convert. Meteorite Silver with Ivory leather. 79k.
    Previously enjoyed: 1970 XL6 4.2 1974; 1982 XJS HE V12 5.3 1987 - 1990; 2000 S Type 3.0 manual 2001-2015; 1998 XK8 Convert Mar/Apr 2016. 2009 Red XK convert Nov 2016 to March 2017: 2010 All black XKR May to Oct 2017: 2009 Green XKR convert. 28k miles.Mar to July 2018

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  4. #13
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    Quote Originally Posted by Alec Escolme View Post
    Did you read the links I posted?
    I read it, yes. Not sure I believe it, though

  5. #14
    Senior Member Stagnite's Avatar
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    Quote Originally Posted by 2woody View Post
    I read it, yes. Not sure I believe it, though
    I am a tad puzzled by your answer. Not really bothered, but puzzled. Do you mean that you think that the OP is fibbing?

    He replaced lots of engine sensors and various parts, did umpteen tests and finally cured the engine misfiring problem when the cats were changed. Seemed quite conclusive to me.
    Currently enjoying:
    2007 XKR Convert. Frost Blue, Ivory leather. 32k
    2006 S Type R. Slate Grey, Dove Grey leather. Full Burr Walnut upgrade, Rear DVD screens. 64k.
    1999 XKR Convert. Meteorite Silver with Ivory leather. 79k.
    Previously enjoyed: 1970 XL6 4.2 1974; 1982 XJS HE V12 5.3 1987 - 1990; 2000 S Type 3.0 manual 2001-2015; 1998 XK8 Convert Mar/Apr 2016. 2009 Red XK convert Nov 2016 to March 2017: 2010 All black XKR May to Oct 2017: 2009 Green XKR convert. 28k miles.Mar to July 2018

  6. #15
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    Quote Originally Posted by Stagnite View Post
    I am a tad puzzled by your answer. Not really bothered, but puzzled. Do you mean that you think that the OP is fibbing?

    He replaced lots of engine sensors and various parts, did umpteen tests and finally cured the engine misfiring problem when the cats were changed. Seemed quite conclusive to me.
    The problem I've got with it is that cats not performing right doesn't affect the running unless they're blocked - in which case it would hardly run at all.

    There are four lambda sensors, two upstream and two downstream of the cats. The upstream ones measure engine performance and adapt (a little) to suit. The downstream lambda sensors measure the cats performance and inform the driver via the MiL if they're not performing well. The downstream lambda sensors do not affect the running of the engine. Ergo, if the cats are damaged, the engine won't notice and certainly won't run any differently. Unless the cats are blocked, but that would as I said result in hardly running at all under all circumstances.

  7. #16
    Senior Member Stagnite's Avatar
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    Quote Originally Posted by 2woody View Post
    The problem I've got with it is that cats not performing right doesn't affect the running unless they're blocked - in which case it would hardly run at all.
    Exactly, but, there will be an interim time when the cats are not totally blocked, but blocked enough to have an adverse effect on the running of the engine when at high revs.

    Cats don't just block up overnight as far as I know.
    Currently enjoying:
    2007 XKR Convert. Frost Blue, Ivory leather. 32k
    2006 S Type R. Slate Grey, Dove Grey leather. Full Burr Walnut upgrade, Rear DVD screens. 64k.
    1999 XKR Convert. Meteorite Silver with Ivory leather. 79k.
    Previously enjoyed: 1970 XL6 4.2 1974; 1982 XJS HE V12 5.3 1987 - 1990; 2000 S Type 3.0 manual 2001-2015; 1998 XK8 Convert Mar/Apr 2016. 2009 Red XK convert Nov 2016 to March 2017: 2010 All black XKR May to Oct 2017: 2009 Green XKR convert. 28k miles.Mar to July 2018

  8. #17
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    I read the threads about the cats and I am going to test them as described above. Ie by getting live data from the 02 sensors. I will also try to test the crank speed sensor. When I get chance to look at my car.

  9. #18
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    Quote Originally Posted by Martynxjr View Post
    I read the threads about the cats and I am going to test them as described above. Ie by getting live data from the 02 sensors. I will also try to test the crank speed sensor. When I get chance to look at my car.
    there are probably two things that you need to bear in mind....

    on these, the four lambda sensors are not the same - wide-band upstream and narrow-band downstream

    and live-data is really not much use - the sensors alternate between a high and low voltage every couple of seconds, so other than telling you that they are functioning, its damn-near impossible to work out how well they're functioning.

    Its going to be best to change the sensors if they're old - I did mine at about 150K miles. Not because I thought they'd failed, but they're really old at that sort of mileage

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