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Thread: 2001 BMW 750 M73 vaccum leak, rough idle questions? (HQ pic)

  1. #1
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    Question 2001 BMW 750 M73 vaccum leak, rough idle questions? (HQ pic)

    Hi Everyone,

    First, I would to apologize for my English writing and naming parts. I have 01 750 v12 bought couple of months and still spending money on it and it's never enough . anyway I'm getting CEL system too lean bank 1 we all know this is a common issue on these engine and mostly a vacuum leak. I did change 12 new spark plugs (without removing intake manifolds) I noticed slightly improvement with morning rough idle and 2 new crank case with rubbers (without removing intake manifolds) no different, I did every thing to avoid removing the intake manifold since it's $$$$ to replace if they are cracked cheapest is $650 on Ebay for 4 sets. I took it to a pro bmw guy and told me that the O2 sensor on bank 1 before cat and thermostat so I replaced the O2 sensor and will replace thermostat soon. he mentioned that the sucking jet pump should not be the way it looks below he said that the hose from brake booster with green numbers should be connected directly to the pipe to EGR.?? when he squeeze or tight the bottom hose under the jet pump idk something happens to the engine feels like the pre owner changed something and I'm not sure what's happening and would like to see who has same engine and show me his diagram for this ?? plus I hear like air leaking from this area and I checked all of them and idk if it is the jet pump it self that's leaking ?? I tried a cheap way to diagnose the vaccum leak. attached a hose to the throttle body pipe and start blowing cig smoke inside and noticed that the smoke coming from the injectors ? yeah I must remove the intake manifold anyway even thought I tried not too. my considering is what it could be causes this leak is it the o-rings and how many should I order 24 ? and what about the hose that's connected to the injector ? plus another issue is RPM when I turn the car on after turned off for couple of minutes the RPM goes high then after a minute it goes down to normal and the car is warmed up ? do I need to worry about this ? could be Temp sensor or thermostat?
    my next project will be refurbish the intake flange gaskets, injectors, VCG, thermostat.

    I listed some pictures and looking forward to hear from you guys and sorry for long writing.









    Last edited by BMW750V12; 02-15-2018 at 08:35 PM.

  2. #2
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    Here's how it should be connected:

    http://www.realoem.com/bmw/enUS/show...29#13531436158

    Squeezing the pipe should make no difference to the engine note or idle-speed. If it does then you have a vacuum leak on some part of the brake booster vacuum circuit. Other model years have a slightly different circuit for the sucking-jet pump - the jet pump is simply in-line between the manifold take-off point and the brake booster - possibly this is how yours has been modified.
    Last edited by Timm; 02-15-2018 at 05:08 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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