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Thread: Rpm Revs upon all starts

  1. #1
    Join Date
    Nov 2022
    Location
    Tennessee
    Posts
    1
    My Cars
    11 BMW 535ix

    Rpm Revs upon all starts

    I have an 11 BMW 535ix base model that fluctuates in revs upon every start, hot or cold weather. The car has a little over 65k miles on it and has always been thoroughly serviced and mostly at local dealership - not that that is a plus.

    No engine light comes on when this happens and I have no OBD that would give me a conclusive answer. Don't even know what the best App is specifically for a BMW.

    I am up to date on all services required plus new iridium Laser plugs. I also had a Dinan Stage One installed several years ago and a quad exhaust system. I am only mildly increasing the performance of the car to the extent that I am modifying with life enhancing and had mileage saving upgrades.

    Two weeks ago I had a VRSF intercooler and aluminum charge pipe installed and am currently looking for the right TDV upgrade compatible with those parts

    I can only judge by the gauge but it looks like I am running about 20% cooler. it seems at first, the car was also running significantly smoother too but now I can not tell that much. Maybe I've just gotten use to it.

    One thing I do notice is that I don't seem to have the immediate turbo punch I had before the IC and charge pipe were put in. Turbo seems to lag and needs to find a speed at which it will respond impactively.

    Which leads me to a very annoying thing that's been happening for year's. (I have had the car since April of 18 with only one previous owner who put 4k miles on it a year)

    So, to reiterate, At every start I have about 15 seconds of up and down revs between 1500 and 500; sometimes on low end is now a fluttering briefly like it's going to stall. Otherwise, driving and stops at idle are smooth.


    I have read the list of things it could be and I am concerned but don't know where to have someone start looking and avoid taking things apart. The cost of testing can be time consuming and expensive and at dealer shop prices, you can easily get jacked around.

    What are the easiest things to check that are most obvious without parts replacement and is this problem a common one with this car - even with meticulous maintenance?

    I would appreciate the best educated advice to a quick fix.
    Last edited by Skysurfer6; 11-23-2022 at 11:28 PM. Reason: Mispell

  2. #2
    Join Date
    Jul 2013
    Location
    Casablanca, Morocco
    Posts
    780
    My Cars
    2001 e46 323i
    I have replied to your questions in blue, within your text.

    Quote Originally Posted by Skysurfer6 View Post
    I have an 11 BMW 535ix base model that fluctuates in revs upon every start, hot or cold weather. The car has a little over 65k miles on it and has always been thoroughly serviced and mostly at local dealership - not that that is a plus.

    No engine light comes on when this happens and I have no OBD that would give me a conclusive answer. Don't even know what the best App is specifically for a BMW.

    There are several cheap OBDII options available for sale, that are not specific to Bmw but will do the job in terms of generic codes to be further investigated. This one claims to offer manufacturer specific diagnosis + the ability to customize a few things... https://www.mycarly.com/plan/?c=MA&b=bmw&n=BMW
    You can also, for free, install a Bmw software on a laptop, requiring only a cheap ($15) OBDII adapter to connect to the car. Not sure if INPA is compatible with your car as it seems to work up to the E60 5 series, but there probably are other softwares available.


    I am up to date on all services required plus new iridium Laser plugs. I also had a Dinan Stage One installed several years ago and a quad exhaust system. I am only mildly increasing the performance of the car to the extent that I am modifying with life enhancing and had mileage saving upgrades.

    Two weeks ago I had a VRSF intercooler and aluminum charge pipe installed and am currently looking for the right TDV upgrade compatible with those parts

    I can only judge by the gauge but it looks like I am running about 20% cooler. it seems at first, the car was also running significantly smoother too but now I can not tell that much. Maybe I've just gotten use to it.

    One thing I do notice is that I don't seem to have the immediate turbo punch I had before the IC and charge pipe were put in. Turbo seems to lag and needs to find a speed at which it will respond impactively.

    When upgrading parts related to the intake or exhaust tract, your ECU needs to be tuned accordingly (unless it's a very mild upgrade, in which case it can adapt to the changes) or it will keep trying to run the old parameters, which could explain the turbo lag, either because of increased airflow, or lower intake temps, or both.

    Which leads me to a very annoying thing that's been happening for year's. (I have had the car since April of 18 with only one previous owner who put 4k miles on it a year)

    So, to reiterate, At every start I have about 15 seconds of up and down revs between 1500 and 500 those 15 seconds could be the time your ECU needs to run adaptations ; sometimes on low end is now a fluttering briefly like it's going to stall. Otherwise, driving and stops at idle are smooth.

    I have read the list of things it could be and I am concerned but don't know where to have someone start looking and avoid taking things apart. The cost of testing can be time consuming and expensive and at dealer shop prices, you can easily get jacked around. That cost will be greatly lowered if you get a scanner and look up error codes yourself, to make for a targeted intervention.

    What are the easiest things to check that are most obvious without parts replacement and is this problem a common one with this car - even with meticulous maintenance? You could swap the old parts back in temporarily to confirm that they are what is causing the issue. Another thing to look for is a small intake leak (which goes away when the engine warms up, as rubber expands when it warms up) or a MAF sensor issue, but again your best bet is a scanner, not only for this particular issue but on the long run as well.

    I would appreciate the best educated advice to a quick fix.
    "If you have integrity, nothing else matters. If you don't have integrity, nothing else matters." Alan K. Simpson.
    5spd E46 "3XX": 328i engine, 330i Intake and exhaust, CAI, 323i diff.

  3. #3
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Welcome to the forum.

    As a rule, you shouldn't ever modify an engine when it's having issues you haven't identified. When you do, you greatly complicate diagnosis.

    You absolutely need to connect to the car with a BMW-specific diagnostic scan tool. You need to know what BMW trouble codes are stored, and you need to be able to see live data.

    Just from the description you give, it would seem that there's an issue with fuel mixtures before the oxygen sensors come online and correct it. But it's possible you have a contaminated MAP sensor, the wrong spark plugs, a failing high pressure fuel pump, a contaminated MAF sensor, or a computer that hasn't been appropriately tuned for the modifications you've done.

    I don't know what "gauge" you're referring to, when you say you're "running about 20 % cooler" . Maybe you have some aftermarket gauge, but the only temp gauge I recall on your car is an oil temperature gauge, which is absolutely not going to be affected by an intercooler swap.

    Also, do keep in mind that "hot-rod" modifications often do exactly the opposite of what's promised in the advertising. FACTORY systems, as conservative as they may be, are designed AS A SYSTEM, and a huge percentage of aftermarket parts ignore that fact, and cause terrible "side-effects".

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  4. #4
    Join Date
    Sep 2006
    Location
    NW suburban Chicago
    Posts
    16,302
    My Cars
    hiss by my window
    "Two weeks ago I had a VRSF intercooler and aluminum charge pipe installed"
    Vacuum leak? Lean mixture, surging idle??
    Agree with the sentiments above.
    Last edited by ross1; 11-25-2022 at 07:34 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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