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s3 with decat but lamba wires are cut?

Discussion in 'A3/S3 Forum (8L Chassis)' started by mrt72, Mar 10, 2013.

  1. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    hi folks, newbie here with a problem.
    just got myself a 2001 s3 and while looking to see if it had a decat ive noticed the wires to the lamba sensor are all cut but no em light on the dash.
    question is, what effect will this have on the car and why would this be done.
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  3. dre_S3
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    dre_S3 Member

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    [Mar 10, 2013]
    Is the lamba sensor after the cat/decat as the facelift has 2 one before the cat and one after, the one after can be mapped out has the car been mapped
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  4. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    supposedly its 262bhp but its very laggy which makes me think its either something wrong or im expecting too much as i had an evo before.
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  5. dre_S3
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    dre_S3 Member

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    [Mar 10, 2013]
    If its 262 it has been mapped mate and that lamba has been deleted because with a decat you would get a light up I think but not 100% the second lamba is only there to tell you the cat is Working so nothing to worry about
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  6. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 10, 2013]
    If the wires on the top lambda are cut then it will be a major issue as the ECU needs this (wideband) lambda to run the engine effectively... if its the post cat lambda (as you have a decat) then no eml would suggest it either been coded out or had a bit of sticky tape stuck behind the dash (happens more often than you think)

    First thing to do is to get a copy of VCDS (there is a link in my sig to a thread that will help you sort this cheaply) and scan for fault codes..

    Not having the post cat lambda connected will typically mean that the ECU will switch off adaptions including potentially live lambda adjustment... the post cat lambda is used for monitoring cat efficiency... its coded out on most stage 2 tuned cars to allow for the fitting of 3" DP's and decats or 200cell sports cats which sometimes throw a fault (and a CEL)...they 'can' be coded out completely but most tuners don't

    <tuffty/>
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  7. dre_S3
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    dre_S3 Member

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    [Mar 10, 2013]
    Yeah I still get a fault code now and thrn with my 200cell cat on will get that sorted when I get the car mapped
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  8. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    so why so laggy if its mapped, running 1.4bar or are they like this, my old golf 1.8t running 220 felt faster
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  9. dre_S3
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    dre_S3 Member

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    [Mar 10, 2013]
    What other mods are on the car ?
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  10. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 10, 2013]
    Depends on what you call laggy... K04's aren't laggy at all if everything is ok... suggests yours has some issues dude...

    Scan for fault codes first, lets get an idea of what going on... then ideally you need to get some logging done...

    <tuffty/>
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  11. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    full powerflow, big front mount and hard pipe kit, did have itg panel filter but ive put a cone on it today, did have forge recirc valve but now has a dv27, full silicone hose kitthink thats about it
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  12. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    the syptoms are when ya floor it the power comes in gradually till 3k then it does put you back in the seat.
    but when you let off the power it also accelerates slightly before backing off.
    plus boost preasure isnt always the same, sometimes boosts to 1.4 others 1.1, so could have boost leak
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  13. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 10, 2013]
    Not familiar with a DV27 but if its an atmos valve bin it... better off just sticking an OE valve on it... what map is on it?

    <tuffty/>
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  14. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    no idea of the map mate, lust got print out saying 262 from rowleys performance engineering.
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  15. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 10, 2013]
    Ok...

    Anyhoo... ^^^ do that :)

    <tuffty/>
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  16. mrt72
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    mrt72 New Member

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    [Mar 10, 2013]
    yeah ill get on it tomorrow and see if it show s anything up cheers.
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