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Thread: Vacuum Hose to the FPR

  1. #1
    Join Date
    Dec 2003
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    Do a stomp test to see what codes it might have as a starting point.
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

  2. #2
    Join Date
    Jun 2006
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    Bethesda, MD
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    Default Vacuum Hose to the FPR

    Wow this is my third "oh ****..." post in the last week. I hate asking without contributing but...

    When I was flushing my cooling system and replacing the thermostat housing, I found that I had somehow broken the hose to the fuel pressure regulator. I notice that that hose is listed on shogun's rough idle and shimmy guide so I figured thats whats caused the rough idle I have now (I jammed the hose back on there but it probably has cracks in it). Basically my car ran smooth and now runs like crap and at idle SERIOUSLY rocks the car. If that vacuum hose had small leaks cause enough of a difference to make the engine run rough accelerating (i though FPR mainly worked during deceleration).

    The reason i'm asking is in this process I also put a lot of pressure on the fuel rail accidentally when pulling the t-stat housing off. I might have broken something on the electrical connection to injector 1, but that seems unlikely. BASICALLY, does it sound like I might be running on 5 cylinders now? Or should I quit asking and just pull the damn fuel rail

  3. #3
    Join Date
    Apr 2006
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    Chicago, Il. U.S.A.
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    First check the connection to the suspect injector. Unplug it, if it doesn't make any difference you have likely found the fault.
    Replace that hose while you're there.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  4. #4
    Join Date
    Dec 2003
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    Good work.

    There are two 3mm vacuum hose lines that connect under the intake manifold. Hose one is your FPR hose; hose two is the one that T's off the valve cover vent.

    If you feel under the base of the intake manifold just behind the block to manifold brace you should find where they connect. If you had a mirror and light, you might be able to see them.

    Can't recall for sure, but you may need to disconnect the fuel hard line mounting bolt at the base of the manifold to make a little extra room. Been a while since I've had to deal with these.
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

  5. #5
    Join Date
    Jun 2006
    Location
    Bethesda, MD
    Posts
    385

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    No codes via stomp test (except for the no codes code). Hm therein lies the problem, how do I unplug the fuel injectors I've sort of got the cover to the fuel rail wiring harness off. I'm going to attempt the bentley procedure for testing fuel injectors (via multimeter).

    Totally disconnecting the vacuum hose doesn't seem to be making the engine run any rougher, i'm still hoping that hose is the only issue. Replacing all vacuum hoses sound like a good idea?

  6. #6
    Join Date
    Jun 2006
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    Bethesda, MD
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    FIGURED IT OUT! Never got that cover off but pried it up enough to see how the injectors are plugged in.. the plug for injector 1 was blatantly out as the electrical connection somehow rotated 90 degrees. Rotated it back... plugged in... car runs normally! yay!

    Still need to replace that hose, still can't figure out where it goes. Disappears through a hole in the intake manifold?

  7. #7
    Join Date
    Dec 2003
    Location
    NW GA
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    261

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    Quote Originally Posted by nirvana19
    FIGURED IT OUT! Never got that cover off but pried it up enough to see how the injectors are plugged in.. the plug for injector 1 was blatantly out as the electrical connection somehow rotated 90 degrees. Rotated it back... plugged in... car runs normally! yay!

    Still need to replace that hose, still can't figure out where it goes. Disappears through a hole in the intake manifold?
    Just replaced mine last week. Go around to the other side of the car and feel up under the intake manifold. You will find the hose after it goes nto the hole you're talking about and then it goes only for another foot or so and plugs into a nipple on what I think is the underside of the throttle body.

    http://www.autohausaz.com/search/pro...ber=6050780581
    1990 535i 5-sp., except for 16" M-Contours, cd deck, and clear corners, completely stock. 226k and running strong

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