Car runs fine, then bogs down, sputters and dies.

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  • cferb
    E30 Fanatic
    • May 2006
    • 1442

    #1

    Car runs fine, then bogs down, sputters and dies.

    I tried searching, found similar, but not the same, I'll continue in a second, but it's important that I figure this out, it's my only car...

    I'll start from the beginning, I don't know if it's related, but we'll see. I was driving along nicely, and a truckmerges directly into me, I honk, down shift and pass him, get about a mile down the road and suddenly I have no power, it's running, but doesn't wanna go when I hit the gas, I turn into the Napa I'm next to(Lucky right? Not so much, they wouldn't even lend me a wrench) as I pull in, it dies, and I roll into a parking spot. I let it sit for a little bit, start it and all is well! I drive the long way through the parking lot, wait for a second for the cars in front to turn, and then I start to go, and it dies again...There is no intermittent sputtering, it just smoothly and slowly dies.

    Now that's all it does, how long it runs is directly correlated to how long it sits. If it sits for about 5 minutes, I can get it to run completely normal for about a minute, then it bogs down, and dies slowly.

    I have replaced in the last couple months
    -Fuel Pump
    -Fuel filter
    -All fuel hoses
    -Spark plugs
    -Spark plug wires
    -Distributor cap and rotor
    -O2 sensor
    -Alternator and belts(I'm 99% this problem is air/fuel related though)

    And I cleaned but not replaced my fuel injectors. I was thinking it was an AFM, but I just so happened to have an m30 AFM sitting around, put that in, and same problem.

    Any ideas?
    sigpic
  • Todd Black 88
    No R3VLimiter
    • Oct 2007
    • 3449

    #2
    main/fuel pump relay. I think its the exact same relay as the horn relay.(orange) swap them and see if that solves it. I think its marked K2? in the fuse box.
    Last edited by Todd Black 88; 06-19-2008, 08:49 PM.
    Originally posted by codyep3
    I hope to Christ you have looks going for you, because you sure as fuck don't have any intelligence.
    2001 silver/Blk 325 cabby. SOLD
    1988 Blk/Blk e30 factory wide body kit car SOLD
    1992 DS/BLK 325 m-tech II apperance pack cabby SOLD!
    2002 325xit Sil/blk. SOLD
    2012 328i xdrive touring. Wht/blk. SOLD
    2009 135 cabby. monacoblue/blk leather SOLD
    2007 Z4m coupe. Silver grey/black/ aluminum. 1of50
    2010 F650gs twin
    2016 M235i cabby. Mineral grey/Red leather

    Comment

    • cferb
      E30 Fanatic
      • May 2006
      • 1442

      #3
      Originally posted by Todd Black 88
      main/fuel pump relay. I think its the exact same relay as the horn relay.(orange) swap them and see if that solves it. I think its marked K2? in the fuse box.
      Same you say? I like the idea of that, so I don't have to buy something I don't need, thanks! I'll check that.
      sigpic

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      • ethree
        E30 Fanatic
        • Aug 2007
        • 1213

        #4
        You might try swapping a known good dme in, if you have one laying around.

        Comment

        • cferb
          E30 Fanatic
          • May 2006
          • 1442

          #5
          The only spare parts I have laying around are the old parts that I replaced...I was thinking the fuel pump relay was the DME? No? I'm new to air/fuel stuff so I don't know much about any of it...
          sigpic

          Comment

          • ethree
            E30 Fanatic
            • Aug 2007
            • 1213

            #6
            dme is just fancy bmw talk for ecu or computer, but it is the brains behind your a/f mixture. I just thought it might be something easy to do to further narrow down your diagnosis.

            Comment

            • e30serg
              E30 Addict
              • Dec 2006
              • 562

              #7
              I would also try checking the CPS. It's easy to remove and clean. Also check the resistance at the plug. Check the Bentley for which pins to check the resistance across.

              Comment

              • jlevie
                R3V OG
                • Nov 2006
                • 13530

                #8
                A bad CPS causes a sudden and complete loss of power, which doesn't sound like what's happening here. A smooth loss of power to a shutoff sounds like a fuel delivery issue, which is best diagnosed via a gauge connected to the inlet of the fuel rail.
                The car makes it possible, but the driver makes it happen.
                Jim Levie, Huntsville, AL

                Comment

                • cferb
                  E30 Fanatic
                  • May 2006
                  • 1442

                  #9
                  Something I just remembered, When I put in my m30 AFM, AFPR and 19# injectors(they aren't in anymore) I couldn't get the fuel pressure higher than stock, so I'm thinking it may be a problem that just got worse over time.

                  ECU would make sense wouldn't it? Doesn't the car run off the ECU only after it warms up?
                  sigpic

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                  • autoninja
                    Noobie
                    • May 2008
                    • 9

                    #10
                    Definitly check your fuel pump relay as ive had a very similar problem, and turns out the relay jumps out a little after a big bump.

                    Comment

                    • jlevie
                      R3V OG
                      • Nov 2006
                      • 13530

                      #11
                      ECU would make sense wouldn't it? Doesn't the car run off the ECU only after it warms up?
                      The DME, aka ECU, is a possibility, but what you describe wouldn't make me want to swap it to start with. There are other possibilities that need to be ruled out first.

                      The engine runs off the DME all the time. it provides spark and injector firing pulses.
                      The car makes it possible, but the driver makes it happen.
                      Jim Levie, Huntsville, AL

                      Comment

                      • cferb
                        E30 Fanatic
                        • May 2006
                        • 1442

                        #12
                        I checked the fuel pump and it didn't seem to be running, so I swapped the old(still good) one back in. I drove to work and back with no problem, not running smooth, but I think that's because I have the adjustable fuel pressure regulator on, and I haven't adjusted it.
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