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Thread: 1995 e34 520i touring stalling problem after 5 minutes

  1. #1
    Join Date
    Apr 2018
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    Romania
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    My Cars
    1995 BMW 520i Touring

    1995 e34 520i touring stalling problem after 5 minutes

    hello,
    i'm here for some ideas, my car is giving me hard times. all started in february. in the winter i drive this car just occasionaly. one day i've started the engine and wait for warm-up in front of my house. after a while, when the engine temperature reached first line on the gauge, suddenly the engine started to idle rough, up and down and stopped. no start for a while, just cranking. rough, rough start after a few tries. because it was cold, i came back next day. the engine started at the first key, everything ok. but after about five minutes symptoms are back. rough idle and stop. in the same time, i've heard a noise from the engine. because i've had this noise to an opel before, it was low fuel pressure to fuel injectors. strange. tested with carsoft 6.5 errors : camshaft pulse generator ( missing, short-circuit, disconnected) and MAF ( hot film missing, disconnected, broken). replaced camshaft sensor and MAF ( from a working car). errors still there after error reset. sometimes gone camshaft sensor error, but always MAF sensor error. still no luck with the second one ( new).
    no time for the car until this month.
    a week ago i've replaced the fuel pump. no luck. the same noise from fuel injectors, engine stalling after 5 minutes. replaced fuel pressure regulator. happy for five minutes, no noise from fuel injectors. after five minutes, engine was stalling like before. after restarting the engine, the noise from injectors is back. . cleaned MAF with wd40 and tested it with 12v. all seemed ok, but not sure if this test is conclusive.
    verified all hoses and all vacuum lines. no other errors except MAF. not sure error is real, disconnecting and reconnecting MAF, the engine has a stall moment but running. i know if MAF is missing, the engine is running in " safe mode".
    last week-end i've disconnected a the vacuum line, the one after the throttle body, when engine was stalling. surprise, the engine stopped stalling, and the idle rpm was perfect. when i cover the vacuum line, the engine is stalling and is trying to mantain constant rpm, fluctuates between 300 and 1500 rpm, but dies.
    at this point, my logic tells me that IAC valve is not suplying enough air to intake, the volume is not constant and the open vacuum line is providing enough air to mantain correct idle speed.
    i will buy a second-hand IAC valve, but my best guess is an electrical problem. seems pretty strange to have a sudden problem with fuel pump, pressure regulator, MAF and camshaft sensor.
    i have Siemens DME 5WK9003/ 1744579. i didn't find full pinout for this DME, to check out MAF to DME wirings for cracks and faults.
    I suspect DME problem, but i do not know how to test further. in a few days i will change IAC and see if the problem is still there.
    if so, i think it's DME or other electric problem. but what is happening when the engine is getting warmer? till then, the engine is running well. if stops, fires up again at first crank. everytime.
    things checked out till now : spark plugs, ignition coils, gas quality, replaced fuel pump and fuel regulator, disconnected all engine sensors ( not critical ones), replaced 2 MAF sensors, replaced camshaft sensor, replaced cracked vacuum lines, cleaned MAF, measured voltage at fuel pump fuse. any ideas? sorry for my english, it's not my native language.

  2. #2
    Join Date
    Jun 2007
    Location
    Lake Elsinore CA
    Posts
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    My Cars
    1991 BMW 525i
    I'm just going to throw this out there but did you check your airbox to see if the filter is clogged? Mice sometimes like to build nests in cars that sit during winter months so that's a possibility.

    Also, you said you changed out your fuel pump and regulator, but did you change or check the fuel filter to see if it is possibly clogged also?

    I"m a big fan of checking the simple and easy stuff first before I start parts swapping.

    You swapped the camshaft sensor and MAF but still get the same errors. That leads me to think you might have a wiring or ground (earth) issue. I can't imagine you swapped two bad parts for two bad parts.

  3. #3
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Sep 2006
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    BFE
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    E34T
    Quote Originally Posted by AntoniuSurlea View Post
    cleaned MAF with wd40


    last week-end i've disconnected a the vacuum line, the one after the throttle body, when engine was stalling. surprise, the engine stopped stalling, and the idle rpm was perfect. when i cover the vacuum line, the engine is stalling and is trying to mantain constant rpm, fluctuates between 300 and 1500 rpm, but dies.
    That is surprising, usually a vacuum leak has the opposite effect.

    at this point, my logic tells me that IAC valve is not suplying enough air to intake, the volume is not constant and the open vacuum line is providing enough air to mantain correct idle speed.
    i will buy a second-hand IAC valve, but my best guess is an electrical problem. seems pretty strange to have a sudden problem with fuel pump, pressure regulator, MAF and camshaft sensor.
    i have Siemens DME 5WK9003/ 1744579. i didn't find full pinout for this DME, to check out MAF to DME wirings for cracks and faults.
    I suspect DME problem, but i do not know how to test further. in a few days i will change IAC and see if the problem is still there.
    if so, i think it's DME or other electric problem. but what is happening when the engine is getting warmer? till then, the engine is running well. if stops, fires up again at first crank. everytime.
    things checked out till now : spark plugs, ignition coils, gas quality, replaced fuel pump and fuel regulator, disconnected all engine sensors ( not critical ones), replaced 2 MAF sensors, replaced camshaft sensor, replaced cracked vacuum lines, cleaned MAF, measured voltage at fuel pump fuse. any ideas? sorry for my english, it's not my native language.
    Try cleaning and visually inspecting the IACV first. Then try running with it unplugged and see if there's a difference.

    Your English is fine, don't worry. It's a lot better than my Romanian

    Do the spark plugs look interesting after it's run badly? Covered in soot or oil, strange colors...? Have you properly checked for intake leaks (smoke test is the best)? Any change when the air intake or coolant temperature sensor (the one for the DME, not the gauge) are disconnected?
    Last edited by moroza; 04-26-2018 at 04:37 PM.

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