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Thread: 1998 750il M73 - Slow Acceleration

  1. #1
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    1998 750il M73 - Slow Acceleration

    Recently acquired a 1998 750il with 70k miles. The car was garaged for 18 years, then outside for the last 2 years. Upon purchase one DME was on the back seat and had been painted black. Using progman I recoded the DME's and Encoded a new EML from a donor. My EML was laden with codes. I also replaced one throttle body that was causing engine failsafe due to mechanical failure. I replaced the fuel filter, pumped out a gallon of gas via relay jump, then added 5 gallons of premium, octane boost and seafoam.

    Temp gauge is not working either. Works in cluster test though..

    The car now runs and idles but takes 30 seconds to reach 60mph. One crank case valve is sucking air, so that is on order. I've had that issue before on a previous 750, so Im positive its not causing the slowness Im feeling.

    INPA Codes to decipher a starting place:

    108 "unterbrechung Dauerversorgung" = Voltage Supply B+, Battery Voltage (battery is brand new)
    140 "motormoment bankvergleich" = Engine Torque - Bank Comparison <----Where do I start?


    21 Ultrasonic sensor front right (wheel sensor?)

    and some EWS codes
    204
    39
    Here's a video showing firsthand sluggishness.

    Last edited by 740ilDuke; 02-13-2018 at 09:56 PM. Reason: more info
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  2. #2
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    Only running on one bank? Try replacing both coils if you have spares.
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  3. #3
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    it must be a throttle body problem try to reset the adaption of the throttle bodys with DIS.

  4. #4
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    I will take that into consideration. I dont have a spare coil, but if I need to nab one to help solve this I will.
    Thank you both for the input!
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  5. #5
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    That's slug slow! Yes, only running on one bank by the sound of it - but rather than guessing use diagnostics:

    http://www.meeknet.co.uk/E38/Diagnostics.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  6. #6
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    2001 DINAN 7, 1998 750il
    That is a great site! Thank you 1000 times for putting it together.
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  7. #7
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    Im away from the car right now, but correct me if Im wrong. The M73 has true dual exhaust right? I did feel the exhaust being emitted from both sides once it was cranked. Just trying to rule out running on one bank.


    Quote Originally Posted by Timm View Post
    That's slug slow! Yes, only running on one bank by the sound of it - but rather than guessing use diagnostics:

    http://www.meeknet.co.uk/E38/Diagnostics.htm
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  8. #8
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    2001 DINAN 7, 1998 750il
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  9. #9
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    2001 DINAN 7, 1998 750il
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  10. #10
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    Quote Originally Posted by 740ilDuke View Post
    Im away from the car right now, but correct me if Im wrong. The M73 has true dual exhaust right? I did feel the exhaust being emitted from both sides once it was cranked. Just trying to rule out running on one bank.
    Mostly true dual but there is a center resonator ahead of the rear axle which allows the sides to mix somewhat. I believe the two pipes inside are perforated with insulating material between them.

  11. #11
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    Yes, the resonator allows the gasses to mix, so you can't tell if one bank has fizzled out from the exhausts. I notice that there is a zero load measurement on the last picture - and 2.3 on the other bank - so one bank isn't running. The smoothness figures need to be taken when the engine is running - unless it was taken and the missing bank is somehow stopping the readings!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  12. #12
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    Crazy. That makes sense - half power.

    So I need to look a the coils to start.

    I thought it was definitely odd I wasnt getting any readings. One DME is the "master" and one the "slave" the
    way I understand it. Im just trying to logically go through this in the right order. This is my crash course on the
    M73 I suppose.
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  13. #13
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    Do you not get any error codes?

    - - - Updated - - -

    Having a look through your diagnostic pages it looks like you are not getting the engine speed reading on one bank - and that would point towards a crankshaft sensor failure - and that often does not leave an error code!

    This is the screen shot:

    Fullscreen capture 14022018 220913.bmp.jpg

    The top left slider should show the engine speed (which is generated by the crankshaft sensor)
    Last edited by Timm; 02-14-2018 at 05:13 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  14. #14
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    I think I shared all the codes on the initial post. Is there a specific program I should use? I have Inpa, InpaQT, DIS 4.4 & 5.? etc.

    Happily there seems to be just one CPS on the V12. And its not awful to get to. So, thats now on the table. Im going up to VA where the car is
    in a couple days to start digging back in.

    Post I found on BB on how to swap CPS. http://www.bimmerboard.com/forums/posts/695769
    Last edited by 740ilDuke; 02-14-2018 at 06:01 PM. Reason: update
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  15. #15
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    Quote Originally Posted by 740ilDuke View Post
    I think I shared all the codes on the initial post. Is there a specific program I should use? I have Inpa, InpaQT, DIS 4.4 & 5.? etc.

    Happily there seems to be just one CPS on the V12. And its not awful to get to. So, thats now on the table. Im going up to VA where the car is
    in a couple days to start digging back in.

    Post I found on BB on how to swap CPS. http://www.bimmerboard.com/forums/posts/695769
    Timm said crank not cam.
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  16. #16
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    ....and a quick check on RealOEM shows that you only have one CRANKshaft sensor - so the lack of an engine speed signal on one bank is probably down to INPA rather than a lack of a signal - the engine would not run at all without the single crankshaft sensor signal. If possible, get the smoothness page back up with the engine running and show me the results...
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  17. #17
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    Quote Originally Posted by Timm View Post
    ....and a quick check on RealOEM shows that you only have one CRANKshaft sensor - so the lack of an engine speed signal on one bank is probably down to INPA rather than a lack of a signal - the engine would not run at all without the single crankshaft sensor signal. If possible, get the smoothness page back up with the engine running and show me the results...
    This thread is about his 1998 750. 750s have two crank sensors due to the dual DMEs.

    http://www.realoem.com/bmw/enUS/show...diagId=24_0696
    Part #11 Qty: 2
    See my E38 parts for sale on eBay: click here!
    PM me here for a 5% discount on any of them!

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  18. #18
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    Good, that leaves the crankshaft sensor being the most likely candidate....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  19. #19
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    They look easy to get to on the tranny, interesting to see how they are situated. Looking forward to checking this out!

    Quote Originally Posted by psjr View Post
    This thread is about his 1998 750. 750s have two crank sensors due to the dual DMEs.

    http://www.realoem.com/bmw/enUS/show...diagId=24_0696
    Part #11 Qty: 2
    - - - Updated - - -

    Not sure what's up with INPA. I'll try the same program on my 740 and see whats up. Id be its not inpa - but who knows!

    Quote Originally Posted by Timm View Post
    ....and a quick check on RealOEM shows that you only have one CRANKshaft sensor - so the lack of an engine speed signal on one bank is probably down to INPA rather than a lack of a signal - the engine would not run at all without the single crankshaft sensor signal. If possible, get the smoothness page back up with the engine running and show me the results...
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  20. #20
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    Swap the sensors, standard V12 procedure when something goes wrong.
    Last edited by XAlt; 02-15-2018 at 02:05 PM.

  21. #21
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    Notice that in my last post I realised that I was looking at the wrong diagram - and the V12 has two crankshaft sensors - and that leaves the highest probability that one of them is at fault
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  22. #22
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    Got it. I see the diagram shows one at 6 oclock and one at 4-5 oclock. If they aren't overly complex to swap, I can "borrow" one from my dads 01' 750 and see how it goes. Definitely thinking its the one bank issue. Rain the next two days, attacking this Sunday all day.
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  23. #23
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    They are held on by a single bolt and have the same connectors - you can pop them both out, swap them over and re-connect - if the problem swaps to the other bank then Bob's y'er uncle....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My Current 840ci Sport Individual
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  24. #24
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    Not to sound like a fool, but is there a way to know if one bank is running or not as is? Since INPA doesn't seem to be registering.
    740iLDUKE
    2001 - DINAN 7 Sport - Stratus Gray - 88k miles
    DINAN Springs, Throttle body, Intake, CAI, MAF & Exhaust / Powder-coated Valve Covers & 750 brakes up front, New M-Pars, Monsoons, NBT Nav/Radio, Dual Pane Glass
    1998 - 750il V12 - Arctic Silver - 71k miles
    Bone Stock.
    @scotthduke on Instagram


  25. #25
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    Quote Originally Posted by 740ilDuke View Post
    Not to sound like a fool, but is there a way to know if one bank is running or not as is? Since INPA doesn't seem to be registering.
    Do you hear six injectors ticking or do you hear 12 injectors ticking?

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