New injectors, now runs lean

  1. Central South Joined: Jun 2006 East Sussex Posts: 3105 VTS :)
    #1
    I originally had these injectors with the supercharger, http://www.gmcmotorsport.co.uk/engin.../prod_610.html and would idle around 14-15 AFR.

    Unfortunately one failed so got some genuine Magneti Marelli IWP069's, http://www.competitionsystems.co.uk/product.php?id=146

    Swapped them over and now the idle is really lean, about 18-19.
    Being the same flow I'm not sure why it's so lean.

    I'm on a 3 plug predator.
    Looking for help/ideas as to what could cause this?
  2. Saxperience Forum Bum Joined: Jul 2010 South Wales Posts: 3078 ZX 16v, 205 GTI, 309 Goodwood, 405 MI16.
    #2
    so you've replaced chinese knockoffs with genuine items, not surprised it needs a mapping session.
  3. Saxperience Addict Joined: Jul 2005 Solihull / Bournemouth Posts: 14233 2015 Lapiz Blue Golf R
    #3
    Could rescale the fuel map?! Andy might be able to do this for you.

    You could have an inlet leak?
  4. Saxperience Post Whore Joined: Dec 2004 Grimsby United Kingdom (England) Posts: 5489 SUPERCHARGED saxo vts
    #4
    If andy willing to re scale it thats good but for gods sake take to rr to get fine tuned before you kick crap out of it.

    I am supprised that there is such a difference.

    How did you find a failed injector.
  5. Central South Joined: Jun 2006 East Sussex Posts: 3105 VTS :)
    #5
    Quote:
    Originally Posted by sexy_gt View Post
    If andy willing to re scale it thats good but for gods sake take to rr to get fine tuned before you kick crap out of it.

    I am supprised that there is such a difference.

    How did you find a failed injector.
    Andy did mention about the required fuel value in tuner studio but its probably not the best option.

    I was surprised by the difference too, didn't expect that big a swing to lean.

    To find the failed one I used an infrared thermometer on the manifold when it was missing then swapped that injector round to see if it moved.
  6. Saxperience Post Whore Joined: Dec 2004 Grimsby United Kingdom (England) Posts: 5489 SUPERCHARGED saxo vts
    #6
    Afr 18-19 i cant imagine it would idle.

    Does it actually run ok? Possible that afr is reading false?
  7. Saxperience Hardcore! Joined: Oct 2008 Birtley Posts: 22253 VTR Turbo, 106 xsi track slag, Transit recovery, B
    #7
    take it for a mapping session.. dont use it until

    for all you know the injector that was fucked has been fucked since it was mapped and the other 3 are/were out by miles

    when one is goosed the other 3 can be over/underfueled drastically and give you the overall AFR that looks good
  8. Saxperience Forum Bum Joined: Jan 2003 Scotland Posts: 3380
    #8
    as already said you must have it mapped to get it right ,but the dif between 14.7 +18 at idle is not very much in volume as there is no power being made .
    it will be less than 6% out to make that sort of dif --but that would be a starting point of map correction
    but you must get it mapped properly -do not rely just on correction
    its always possible other things have changed as well since mapped
    If you have w/band gauge then run it up the road at low power and see what it shows -18.1 on cruise and very light load will not destroy and engine and a quick blast as in a couple of runs to save 6k , watching gauge will be ok --but only do this if you have w/b afr gauge to see whats going on
    you may find its only idle thats wrong -- cos idle volumes are so low a very small dif in fuelling can show big dif.even change in tps ostion sensor can cause this amount of change