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Thread: MPS6 Strange Starting Issue

  1. Default MPS6 Strange Starting Issue

    Hi All,

    Whilst this has only happened 3-4 times over the past few weeks I figured I would see if anyone else has had a similar issue so I can catch it early before it ends up with me being stranded or causing some damage. The car is a 2006 Mazda 6 MPS.

    Upon attempting to start the car after being dormant for several hours (e.g. overnight), the intiial attempt to start has failed with the engine cranking over briefly, then conking out. It has always started fine on second attempt, several seconds later, although something i found strange was that rather than going to the standard cold start idle (of about 1900 rpm), instead it idles at around 1100-1200 rpm before dropping to normal idle.

    From a battery point of view it seems to be fine and it doesnt sound like its struggling to crank from a flat battery ( i will test voltage when iget some batteries for my multimeter but am confident its not battery related).

    I replaced the spark plugs, oil, oil filter and air filter recently (<10k ago).

    My first thought was this was due to me being to quick to start the car before the fuel pump builds up pressure after dropping overnight however today it happened again after leaving the key in the on position for a few seconds (pretty sure I can hear the fuel pump going off).

    Has anyone else had similar symptoms? or do they know what might be the cause?
    The strangest thing to me is why it idles at a lower revs on cold start when this happens. Other than the few times this has happened the car seems perfectly fine.

    Any guidance would be much appreciated.

    Cheers

  2. #2

    Default

    Sounds like you have a vacuum leak
    Have you done a boost leak test?

  3. Default

    I havent done a boost leak test (anyone know any good palces in northern suburbs or south eastern suburbs. Mazda dont do them apparently).
    If it were a vacuum leak or a boost leak would the issue occur all the time?

    I will double check for obvious hose disconections etc.

  4. #4
    Join Date
    Aug 2011
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    Sydney North
    Posts
    441

    Default

    DIY boost leak tester. Google DIY version. One of the best things I ever made! Piss easy too!

  5. Default

    Hrmm Ill give it a go. I still dont believe its a boost leak (I would assume a boost leak would cause issues more often and be more noticeable when on boost), but I'll give it a go anyways.

  6. #6

    Default

    As easy as it is to make a boost tester yourself, one would need a air compressor at home (or access to one), in order to be able to test......

    Sent from my Galaxy Nexus using Tapatalk

  7. #7

    Default

    Check all wiring plugs and clean them with contact clean, give the MAF a clean while your at it, Will prob not solve the problem but it is always good to do. +1 on vacuum issue.

  8. Default

    would a boost leak test identify a vacuum leak?

  9. #9

    Default

    Check EGR valve. Guaranteed it is the problem child.
    Give it a good clean, while you are at it, clean the piping.

  10. #10

    Default

    Quote Originally Posted by discodave View Post
    would a boost leak test identify a vacuum leak?
    Yes - you're adding high pressure into your intake system so if there's any air getting out, there will be air getting in.

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