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Thread: Drastic power cut under hard acceleration

  1. #1
    Join Date
    Dec 2018
    Location
    Ohio
    Posts
    10
    My Cars
    1987 325 convertible

    Drastic power cut under hard acceleration

    I’m the new owner of my 1st bmw...a 1987 325 convertible with i think a gt35/t70 turbo.i experienced a massive power cut off under hard acceleration a couple times.like it falls flat on its face for just a second then its back on.i thought maybe that’s what happens when you hit the rev limiter but then I actually did hit the limiter and it reacted and sounded as I would’ve expected.im not sure if it’s overboost cut off or what?but it doesn’t seem right.ive only had the car for a few days and other than those couple incidents and a rough idle it seems to run good.im a newbie but I need to know if it’s something really wrong or my controllers just set too low?it didn’t really seem to be that high of an rpm when it happened and it doesn’t do it if I come up to rpm a little slower.any ideas?b

  2. #2
    Join Date
    Apr 2006
    Location
    Minnesota eh?
    Posts
    6,155
    My Cars
    86 325es
    What motor and ECU is in the car? What you describe does sound like overboost cut.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  3. #3
    Join Date
    Oct 2012
    Location
    washington, dc
    Posts
    1,162
    My Cars
    96 E36 Vert 03 E39 M5
    Curious about your sparks and coils . Have you replaced any plugs since you got it? Have you tried reading the plugs ? Any data logging or are you chipped ? Could be a fuel issue or boost leak also . Have you tried pressuring the intake tract and tested for pressure leaks ?


    Sent from my iPhone using Tapatalk
    http://www.bmwmregistry.com/detail.php?id=13792
    * E39 M5 SterlingGray -RIP 11/2018
    * E36 328 vert Schwarz - ~TurboProject underway
    * E90 335i Sedan MonocoBlau - Daily ToddlerTaxi

  4. #4
    Join Date
    Dec 2018
    Location
    Ohio
    Posts
    10
    My Cars
    1987 325 convertible
    I have not done all those things yet,however ,today I cleaned my idle control valve and throttle(chasing idle surge)idle improved a little and so did fuel cut.i thought it was gone as it didn’t happen until I was really running it hard.so maybe I had leakage and maybe still have some more.i will try to check whole system for leaks as well as plugs/wires.i was thinking why not get a lighter waste gate spring?its got plenty of power.plus I want an air filter so maybe that will help with the cut too?

    - - - Updated - - -

    It’s a 1987 e 30 convertible 325 with 2.5l six.i think it’s a gt35 turbo and megasquirt 2 ignition and fuel control.distributor has been replaced with coil pack

    - - - Updated - - -

    It’s a 1987 e 30 convertible 325 with 2.5l six.i think it’s a gt35 turbo and megasquirt 2 ignition and fuel control.distributor has been replaced with coil pack

  5. #5
    Join Date
    Nov 2008
    Location
    Indiana
    Posts
    2,121
    My Cars
    97' 328is, 07' Titan
    Electronic boost control? If so what is the overboost protection set to? If using closed loop boost control, in the colder weather you can hit higher boost numbers sometimes. I have my overboost protection at 17 psi and normally run 14.5, in this weather I hit 17 easily.
    Last edited by somebody5788; 01-04-2019 at 12:35 AM.
    1997 328is - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, DKM Organic Twin Disc Clutch, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Mishimoto Rad, Devils Own Meth, Porsche 911 calipers with E46 M3 rotors, Corsa Exhaust

  6. #6
    Join Date
    Oct 2012
    Location
    washington, dc
    Posts
    1,162
    My Cars
    96 E36 Vert 03 E39 M5
    U can check for vacuum leaks with some starter fluid .. spray lightly around your hoses intercooler piping etc . Also vacuum lines any catch can or pcv you have . That’s cheap and can be done just don’t smoke while you’re doing it haha


    Sent from my iPhone using Tapatalk
    http://www.bmwmregistry.com/detail.php?id=13792
    * E39 M5 SterlingGray -RIP 11/2018
    * E36 328 vert Schwarz - ~TurboProject underway
    * E90 335i Sedan MonocoBlau - Daily ToddlerTaxi

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