Results 1 to 4 of 4

Thread: 2-1/2 Years and I’m still trying to solve my 1984 733 Problem! (Long Post)

  1. #1
    Join Date
    Jun 2015
    Location
    Wilmington, NC, USA
    Posts
    145
    My Cars
    91 735, 84 733, 84 633

    2-1/2 Years and I’m still trying to solve my 1984 733 Problem! (Long Post)

    1984 733 129K

    533 and 633 should be the same. (apologies to moderator for posting on the other boards . . . . I'm desperate!)


    Yes, I have posted about this before but I have done more work and tried to summarize more accurately.

    I have owned this car for many years. It was runningwell. I was driving in town. It was idling OK at a stop light. When the light changed I had to accelerate in second gear to merge into a lane. The light ahead changed and I had to lift off suddenly and get on the brakes to stop.When I stopped the car almost stalled. It was running extremely rough, would hardly idle and would not accelerate. I was able to limp home in first gear.
    I have worked on this problem on and off for over 2-1/2 years and have not been able to resolve it!

    It starts OK but idles very rough:

    It is running way too rich at idle. It will eventually stall. All 6 spark plugs are black and wet.

    It is possible to speed up the engine by manipulating the gas pedal. Between about 1800 and 2200 RPM with a light load, it runs smooth and if you run it like that for a few minutes, shut it off and remove the spark plugs they are clean and dry.

    You can drive it in the neighborhood with difficulty,with a light foot on the gas and holding it in first. Once the RPMs reach about 2000 it runs OK and can be accelerated and decelerated a little, sounds normal but if you lift off the gas, the exhaust pops and crackles on the overrun which is not normal.

    The fuel delivery is not adjusting for some reason:

    - Too rich at idle, low speed and light load.


    - About right between 1800 and 2200 RPM and light load.


    - Misfires at higher RPM and heavier load – My guess it’s too lean under these conditions.


    -Problem is about the same hot or cold.

    -Compression test. All in spec per Bentley.


    -Eliminated vacuum leaks. (Smoke test). No difference.


    -Problem the same, with or without a foot on the brake.


    - Replaced fuel pressure regulator with OEM years ago, still looks new, not many miles on it.

    Fuel pressure is normal at idle per Bentley, (gauge at fuel rail). Return is not blocked.

    -Disconnected fuel to cold start injector. No change except hard to start when cold.


    -Changed out idle control valve with aftermarket ICV (metal with an adjusting screw, original

    VDO is plastic with no screw). Has 12V at connector, clicks when you apply 12V but doesn't
    “hum” or “vibrate.” Does not change the idle, connected or not connected, new ICV or oldICV.

    -Changed out thermo time switch and temperature sensors*

    (* ECU sensor new, others not new, all checked per Bentley)

    -Changed out idle control module behind glove compartment. If the ICM is connected the car

    starts and idles badly. If you disconnect it, it won't idle at all.

    -Checked TPS. Good according to Bentley.


    -Removed exhaust system. No difference, just loud.


    - I replaced AFM with new one probably over 10 years ago but only about 20K on it. Still looks
    new.
    Tested AFM (Bosch 9V battery test). Voltage changes smoothly when door/flap is opened and closed.

    -Visually inspected DME (Seimens): All harness connections and chip connection clean and DME looks fine inside. Tiny fuse is OK, reinstalled with DeOxit on the connections.


    - Changed out the ECU (Bosch), I have an identical spare, NOS and never been driven on the road. No difference.

    I have not checked the pin connections to the ECU for continuity according to Bentley and I need to do that.

    - I have checked every electrical connection I can think of and re-connected with DeOxit, nothing looks corroded,in fact it looks pretty good considering its age.


    Finally, here are a couple of things that may be clues:

    1. Youtube video of idle here:
    https://www.youtube.com/watch?v=SoTyLaXVbHE
    This is idling, foot off gas pedal.
    Note "swinging pendulum" vacuum gauge.

    2. Like most old E23s, mine leaks when it rains. Wehave had several weeks of warm dry weather and the interior of the car hasfinally dried out. It
    seems to run better. Not running right, but better, alittle more drivable, I was able to drive it around the neighborhood this week for the first time in 2
    years.


    Has anyone encountered a similar problem with moisture in the car?


    Does anyone near Coastal North Carolina have a parts car that runs, and would consider swapping out some parts such as AFM and FPR? I’m prepared to pay fair price for used parts or work out some agreement but I’m reluctant to throw money and new parts at this without any idea what the problem is.

    Thank you for your patience reading this long, complicated post. All help is much appreciated! John Kenneth

  2. #2
    Join Date
    Mar 2013
    Location
    USA
    Posts
    465
    My Cars
    E21/early e23/e34
    Condition of cap/rotor & plug wires? Also, on the ICM, did you replace with a known good unit/new?
    I think you still have a vac leak...

  3. #3
    Join Date
    Jul 2018
    Location
    puerto rico
    Posts
    5
    My Cars
    1984 e23 733i
    Check if your car have engine oil in the rotor and ignition cap. If this is happening you have to change the camshaft seal. My 1984 733i had a very similar problem and that was the cause!!!!!
    Last edited by alosorio; 10-12-2018 at 10:43 PM.

  4. #4
    Join Date
    Jun 2015
    Location
    Wilmington, NC, USA
    Posts
    145
    My Cars
    91 735, 84 733, 84 633
    This thread is still alive! I'ill check, had same problem with a VW starter years ago so I understand what you are sying

Similar Threads

  1. Solve shaking mirror problem (Mirror conversion kit)
    By LLuke in forum 1983 - 1991 (E30)
    Replies: 4
    Last Post: 09-23-2003, 09:36 AM
  2. valentines day 2003 long post sorry
    By Federico in forum Off-Topic
    Replies: 11
    Last Post: 09-18-2003, 12:15 PM
  3. Help me solve this problem
    By fast330 in forum Forced Induction
    Replies: 8
    Last Post: 06-05-2003, 10:49 PM
  4. How long should stock suspension last? years/miles
    By David in forum 1991 - 1999 (E36)
    Replies: 2
    Last Post: 02-06-2003, 07:10 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •