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Thread: RPM fluctuations on '98 740iL?

  1. #1
    Join Date
    Dec 2011
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    Arnhem, Netherlands
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    1998 BMW 740iL

    RPM fluctuations on '98 740iL?

    Hi guys,

    I have some strange RPM fluctuations in my '98 740iL while driving at lower speeds/RPMs.
    - Driving at about 50km/h, RPM is around 1100: When I have steady throttle to maintain this speed, the RPMs start to move from 1000-1200 RPM. This is hearable and is also feelable in the car as a light shake.
    - When driving about 80-100km/h and I let go of the throttle and let the car slow down on her motor. RPM dips heavily for about 500-1000 RPM, like the car wants to shift down, but doesn't. This usually repeats a few times before speed is too low. This happens in D, S and also the lower gears in M.
    - Not really a fluctuation, but something that might be connected. Driving at around 2k RPM, trying to accelerate a little, I hear a sound from the Airbox, like the car needs a lot of air all of a sudden. It's very brief, but can happen multiple times after eachother.

    Car accelerates ok. Fuel consumption is good.

    This all happens when the engine is hot. No codes in INPA.

    Things done already:
    - Torque converter has been revised, new lockup ring
    - OSV replaced
    - MAF replaced 10k KM ago

    Could this be the utcgs and vcgs? O2's? Any help is appreciated.

    I'll try to get something caught on camera this weekend. For extra illustration sake. Also will try to disconnect the MAF, for exclusion sake.

  2. #2
    Join Date
    Feb 2011
    Location
    IL
    Posts
    13,581
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    2000 740i sport
    Is maf bosch? Check your analog values with inpa for an unmetered vacuum leak... Also check under hood for vacuum leak...

  3. #3
    Join Date
    Dec 2011
    Location
    Arnhem, Netherlands
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    1998 BMW 740iL
    Yeah, MAF got replaced by indy who only works with OEM parts. And like we were discussing in this thread, I have the same "extreme" MAF values as you have.

    Also tried to find vacuum leak (sprayed brake cleaner like the vid Edwin made) but couldn't find any. Could a vacuum leak result in these "malfunctions"? Thought it only was a rough idle?

  4. #4
    Join Date
    May 2010
    Location
    Brownsville Texas USA
    Posts
    112
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    95 e38 98 e39- 00" e38
    well....try to check the MAF...If this MAF send the correct signal-voltage to the TCU or ECM......then you saiyn that you check the torque converter, for this case you should take down the transmission, ok try to make shure that find a mechanical outside the tranny or electroci failure with the TCM.....My brother works in a transmission shop in Houston TX USA and he tell me a couple of tips to find failure..here we go......

    1. Stop the car....then drive the car but dont pass the 1500 RPMS and make the car shift all the shifts on D.....if you get all the shifts and you not feel that shakeness probably could be outside mechanical problems such as transmission supports, drive shaft, drive shaft support, the bearing of the drive shaft etc etc . but nothing inside the tranny.

    2.- Stop the car...then drive the car but dont pass the 1500 RPMS and make the car shift all the shifts in D....when you touch the 50-65 KMs, shift the tranny to neutral....If you still feeling the shake it will be 99% shure that is a mechanical outside-tranny problem...but, if you shif to N and the shakness stop, the could be something else like Inside-tranny problem such as many things (oil-filter-valves-solenoids etc etc ) or TCM issues...and theres when you could get codes and follow the failure of the codes you get and probably could be a one solenoid, or on cable inside the tranny that nos passing signal etc etc .......

    This is a humble advice of a bimmer driver....jijijijij....best regards

  5. #5
    Join Date
    Dec 2011
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    Arnhem, Netherlands
    Posts
    56
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    1998 BMW 740iL
    Thanks Ernesto, I'll give that a go.
    Made a little clip showing 2nd and 3rd point. Figures though why I didn't become a cameraman...

    [ame="http://www.youtube.com/watch?v=x-FcSMqPtbg"]http://www.youtube.com/watch?v=x-FcSMqPtbg[/ame]

  6. #6
    Join Date
    Nov 2011
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    Canberra, ACT, Australia
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    2001 735iL Individual

    Lightbulb

    I need to learn how to post a clip, nice job. Look, I just want to throw this into the mix.

    I notice that you're in D mode. When I drive around in Sport mode, I'm finding it difficult to get used to the not so subtle 'fluctuations' that that mode performs sometimes - upshifting later aside - my ride does slip between gears noticeably (mainly rpm increases as it down shifts) without input from me, could be gradients or trying to maintain speed with cruise on (that's annoying on S mode). In S mode, a sudden release of throttle will cause a downshift. A slight uphill gradient will cause a downshift.

    So, could the car be dropping into S mode for some reason? Without any indication?

    The "noise" you refer to may mean my 2c is meaningless.

    -Stu
    GH62 Entwicklung 38
    _
    2001 face-lift 735iL L810A AUS RHD, 940A Individual; 336 Metallic Agaischblau / Aegean Blue; O7OY Montana Pearl Beige leather; 0118 Arizona Sun Maple wood trim; M62TUB35; 5HP24 (A5S440Z) 202A Steptronic; prod 2000/05/12; build 07/00; 110,000 Km / 68,000 m
    _
    Factory staggered Style 42 Kreuzspeichen-Verbundrad II (cross-spoke composite 2): 8J 255/45/18 ContiSportContact 2 | 9.5J 285/40/18 Nitto 555
    _
    216 Servotronic; 508 PDC, 220 SLS & 210 DSC; 204 Short Final Drive 3:15:1; AIC; 602 16:9 TV/609 Mk III SatNav; 627 Nokia 3110; 320 de-badged; 456 / 495 / 488 16-way Comfort Seats; 245 electric steering column; 358 climate comfort windscreen; 431 interior mirror auto-dip; 500 intensive cleaning headlight washers; 522 Xenon; 620 voice control; 694 6-CD; 676 HiFi; 710 Nappa Navy Blue "M" leather M/F SW; 778 Individual sills; 785 clear corners
    _
    Sport HSTC; speed delim
    _
    E32 730i | 3.0 V8 M60B30; 2007 SE FXDL

  7. #7
    Join Date
    Dec 2011
    Location
    Arnhem, Netherlands
    Posts
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    1998 BMW 740iL
    I don't use that many cruise tbh. Highways here are too crowded to have it on all the time..

    Would be weird if the car drops in S. Although the RPM drops are there in S as well, and in M2+M3.

  8. #8
    Join Date
    Nov 2011
    Location
    Canberra, ACT, Australia
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    2001 735iL Individual

    Smile

    I'm not sure my comments have anything to do with your problem but if I sense something from my limited experineces I'll do a post and maybe some of the more experienced members can connect a few dots. In my short time here I've read that many things can go wrong and intuition is not always helpful. That said, I hope this can be diagnosed or identifed easily and quickly.

    -Stu
    GH62 Entwicklung 38
    _
    2001 face-lift 735iL L810A AUS RHD, 940A Individual; 336 Metallic Agaischblau / Aegean Blue; O7OY Montana Pearl Beige leather; 0118 Arizona Sun Maple wood trim; M62TUB35; 5HP24 (A5S440Z) 202A Steptronic; prod 2000/05/12; build 07/00; 110,000 Km / 68,000 m
    _
    Factory staggered Style 42 Kreuzspeichen-Verbundrad II (cross-spoke composite 2): 8J 255/45/18 ContiSportContact 2 | 9.5J 285/40/18 Nitto 555
    _
    216 Servotronic; 508 PDC, 220 SLS & 210 DSC; 204 Short Final Drive 3:15:1; AIC; 602 16:9 TV/609 Mk III SatNav; 627 Nokia 3110; 320 de-badged; 456 / 495 / 488 16-way Comfort Seats; 245 electric steering column; 358 climate comfort windscreen; 431 interior mirror auto-dip; 500 intensive cleaning headlight washers; 522 Xenon; 620 voice control; 694 6-CD; 676 HiFi; 710 Nappa Navy Blue "M" leather M/F SW; 778 Individual sills; 785 clear corners
    _
    Sport HSTC; speed delim
    _
    E32 730i | 3.0 V8 M60B30; 2007 SE FXDL

  9. #9
    Join Date
    Dec 2011
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    Arnhem, Netherlands
    Posts
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    1998 BMW 740iL
    Intuition is usually right, but a bit of help of Google or these boards ofcourse.

    Though, no one seen this before?

  10. #10
    Join Date
    Nov 2011
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    Canberra, ACT, Australia
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    2001 735iL Individual

    Lightbulb hard reset - gremlins

    Quote Originally Posted by nuxy View Post
    Though, no one seen this before?
    PM one of the Moderators on this board? They're busy and try to answer everything.

    Many issues are apparently solved by a 'hard reset'. I'm not suggesting you do this but rather search and consider.

    I have a gremlin issue of my own making but haven't done the hard reset because my ride needs to be driveable tomorrow for a brake job.

    Basically:

    • park it securely
    • turn off the vehicle
    • open the boot / trunk from the cabin (or get out and buzz it or key it open)
    • lights off, get out, close all doors
    • wait at least 16 minutes
    • observe that, at least, the CD/DVD/SatNav stuff in the boot /trunk have switched off - no lights, no whirring;
    • no other lights or noises (don't sneeze or cough - something may light up and you have to wait 16 mins again ... electronic BM joke)
    disconnect the leads from the battery, -ve earth first, then +ve (thousands will argue but it's -ve first)

    wait 5 mins (because IcemanBHE says so)

    touch leads briefly (ditto)

    then reconnect +ve then -ve

    You may have issues at first, there's a little [very good] argument about whether it works on all E38s or not; some say 100 miles of driving - implying that the system is relearning while 'on' and moving, some say 24 hours laid up - implying that something's powered even though the car is 'off' after 16 mins. I favour driving it until it it comes 'good', if it's going to eliminate any gremlins by a hard reset.

    If I ever get any more gremlins and if I have a free weekend I'll try it and see what happens.

    my gremlin

    http://forums.bimmerforums.com/forum....php?t=1773583

    Stu
    Last edited by Stu735iL; 01-18-2012 at 07:54 AM. Reason: link to my gremlin
    GH62 Entwicklung 38
    _
    2001 face-lift 735iL L810A AUS RHD, 940A Individual; 336 Metallic Agaischblau / Aegean Blue; O7OY Montana Pearl Beige leather; 0118 Arizona Sun Maple wood trim; M62TUB35; 5HP24 (A5S440Z) 202A Steptronic; prod 2000/05/12; build 07/00; 110,000 Km / 68,000 m
    _
    Factory staggered Style 42 Kreuzspeichen-Verbundrad II (cross-spoke composite 2): 8J 255/45/18 ContiSportContact 2 | 9.5J 285/40/18 Nitto 555
    _
    216 Servotronic; 508 PDC, 220 SLS & 210 DSC; 204 Short Final Drive 3:15:1; AIC; 602 16:9 TV/609 Mk III SatNav; 627 Nokia 3110; 320 de-badged; 456 / 495 / 488 16-way Comfort Seats; 245 electric steering column; 358 climate comfort windscreen; 431 interior mirror auto-dip; 500 intensive cleaning headlight washers; 522 Xenon; 620 voice control; 694 6-CD; 676 HiFi; 710 Nappa Navy Blue "M" leather M/F SW; 778 Individual sills; 785 clear corners
    _
    Sport HSTC; speed delim
    _
    E32 730i | 3.0 V8 M60B30; 2007 SE FXDL

  11. #11
    Join Date
    Dec 2011
    Location
    Arnhem, Netherlands
    Posts
    56
    My Cars
    1998 BMW 740iL
    Isn't that like the same as clearing adaptations? I've done that doesn't help much, only makes the car a bit more "peppy".

  12. #12
    Join Date
    Nov 2011
    Location
    Canberra, ACT, Australia
    Posts
    432
    My Cars
    2001 735iL Individual
    't'was just my 2c, don't know more that what I said, except to add that it can fix some unusual issues, sorry.

    -Stu
    GH62 Entwicklung 38
    _
    2001 face-lift 735iL L810A AUS RHD, 940A Individual; 336 Metallic Agaischblau / Aegean Blue; O7OY Montana Pearl Beige leather; 0118 Arizona Sun Maple wood trim; M62TUB35; 5HP24 (A5S440Z) 202A Steptronic; prod 2000/05/12; build 07/00; 110,000 Km / 68,000 m
    _
    Factory staggered Style 42 Kreuzspeichen-Verbundrad II (cross-spoke composite 2): 8J 255/45/18 ContiSportContact 2 | 9.5J 285/40/18 Nitto 555
    _
    216 Servotronic; 508 PDC, 220 SLS & 210 DSC; 204 Short Final Drive 3:15:1; AIC; 602 16:9 TV/609 Mk III SatNav; 627 Nokia 3110; 320 de-badged; 456 / 495 / 488 16-way Comfort Seats; 245 electric steering column; 358 climate comfort windscreen; 431 interior mirror auto-dip; 500 intensive cleaning headlight washers; 522 Xenon; 620 voice control; 694 6-CD; 676 HiFi; 710 Nappa Navy Blue "M" leather M/F SW; 778 Individual sills; 785 clear corners
    _
    Sport HSTC; speed delim
    _
    E32 730i | 3.0 V8 M60B30; 2007 SE FXDL

  13. #13
    Join Date
    Dec 2011
    Location
    Arnhem, Netherlands
    Posts
    56
    My Cars
    1998 BMW 740iL
    Decided to keep on driving and trying to avoid the annoying stuff about the car. Gotta enjoy driving her, without nitpicking about everything, right?

    Although if someone has/had the same, and has a fix for it, I'm open for anything.

  14. #14
    Join Date
    Nov 2008
    Location
    Amsterdam NL
    Posts
    19,644
    My Cars
    735i 2001 E38
    If you are in the area (Huizen) I can look at it for you.

    Have some experience with the E38

    Dus stuur me ff een PB

    Have a technical question, don't send me a PM but post it on the board so others can benefit from it!

  15. #15
    Join Date
    Jan 2013
    Location
    Fargo,ND
    Posts
    4
    My Cars
    1998 BMW 740il
    Hey Nuxy,
    Did you ever found the solution for this issue. I am fighting this rpm fluctuation, rough idle, grinding noise for 4 years. I changed all the intake gaskets, pcv valve, throttle body gaskets, valve cover gaskets, new ICV, new Maf, new vaccume lines. everything under the hood it checked for vaccume leaks.
    I have two 1997 740is . One had the same noise and rpm fluctuation because the valve cover was leaking pretty bad. after replacing the valve cover, it run like butter. But the other one is still a mystery.
    Please let me know if anybody found the solution for this.
    I have 207,000 on the flagship. I want to put half million miles on this. that's the goal

    Thank you

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