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Thread: weird smoke on start up

  1. #1
    Join Date
    May 2008
    Posts
    16

    Default weird smoke on start up

    Hi Guys I posted a while ago about excessive smoking on start up..not just in the morning, even on start up after being left for an hour or so - which is a clue, if the guides were that worn as to smoke after such a short time, I would get smoke after coasting in gear and re applying the throttle - but it doesnt!?

    It's a 94 540i/6 with engine replaced by bmw. The wierd thing is that the smoke does not smell of oil at all...in fact is smells like paint or diesel (I do know what burning oil smells like btw) Also last week it did not emit this smoke at all and now its back again.

    I've done all the gaskets, pcv, oil pump etc etc

    The history file shows new fuel lines earlier this year...could the garage have done something wrong there?? When it emits in the morning it usually stalls as the smoke is coming out? I know, I know you're thinking the engine is toast but it just isn't!! I've had too many cars and worked in my fathers garage for too long to know that this simply isnt a worn engine, if it were that worn it would smoke under load, this is clean as a whistle under load, plus the fact that it stalls makes me think it's fuel related...could it be a leaky injector? it's blue/black smoke..and it floats away quickly not like oil smoke which hangs in the air

    Removing No8 plug reveals no real colour difference to the other plugs so I tend to rule out bore wear on that basis not to mention the fabulous performance and fuel economy, but I know there isn't a lot else that could be causing this smoke

    Anyone have any ideas on this most strange one? P.S - the engine air temp sensor is apparently reading too hot so I'm fitting a new one tommorow...could that be related? I though maybe if the ecu was getting the mixture totally wrong then, maybe....I dunno
    Last edited by dog man; 07-10-2008 at 07:45 AM.

  2. #2
    Join Date
    Oct 2005
    Posts
    518

    Default

    A leaky injector is a likely suspect, as you mentioned. If it leaks, you'll have a very rich start up with some gray/black smoke that smells of gasoline or rotten eggs. If an injector is leaking, you will also lose fuel pressure and it'll crank over more than usual on start up. If your ECU was reading a higher than actual temperature, it wouldn't have the symptoms of a rich running engine.

  3. #3
    Join Date
    Apr 2006
    Location
    Chicago, Il. U.S.A.
    Posts
    4,243

    Default

    Agreed. You may be able to pipoint the one by using the screwdriver stethescope to hear which injector sounds soft.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  4. #4
    Join Date
    May 2008
    Posts
    16

    Default

    Cool thanks guys, have fitted the new temp sensor anyway as I knew it was reading to high.

    I will check the injectors and re post! thanks again!

  5. #5
    Join Date
    May 2008
    Posts
    16

    Default injectors

    I'm finding it a little bewildering the array of injectors on offer. I want to get a whole set but I'm unsure which ones are correct for the 4.0 M60 can anyone set me right....


  6. #6
    Join Date
    Apr 2006
    Location
    Chicago, Il. U.S.A.
    Posts
    4,243

    Default

    http://www.realoem.com/bmw/showparts...85&hg=13&fg=15
    #7 There are also lots of places that will sonic clean, test and replace the filters and o-rings for ~$20 a throw.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  7. #7
    Join Date
    May 2008
    Posts
    16

    Default

    Thanks Ross!

  8. #8
    Join Date
    May 2008
    Posts
    16

    Default

    Okay stock injectors cleaned/reconditioned. The report? oil deposits and 'normal' wax build up. The result is it still smokes on startup but I experimented the other day - I ran her out of fuel and left her overnight. In the morning with fresh petrol it started with no smoke?

    This is a strange problem

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