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    4.4L engine "pulses" at low throttle

    I have an 05 x5 with 4.4L and have recently noticed that the engine pulses when cruising at very low throttle openings (35 - 40 mph). By pulses, what I am actually observing is that the engine seems to cut out for about half a second at odd intervals ranging from once every 10 seconds to once every 20 seconds. If I depress the throttle further, everything seems normal. Acceleration etc. all seem normal. I suspected it might be dirt on the MAF so I cleaned it per instructions with MAF cleaner. No change. The feeling is almost like I lose ignition momentarily but I am assuming that if that were the case and I had unburned fuel in the exhaust I'd be getting CEL codes and I'm not. I have noticed my fuel economy average has dropped to about 18.5 from 19.1 but that could just be seasonal. I'm guessing it might be a problem related to malfunction in the throttle position sensor but I don't know anything about that part on this motor and am hoping someone more familiar can weigh in with some diagnostic thoughts or some repair pointers.

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    Member No: 65681 66.cobra is an unknown quantity at this point 66.cobra's Avatar
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    have you checked??????

    fuel filter-replace
    plugs-check gap and electrode condition and replace if needed
    coils-look for cracks or oil in the galleys from leaking valve cover gaskets.<B>
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    Re: have you checked??????

    Hi. Thank you for the ideas. The fuel filter might be ready for a replacement. I'll check into that. 52K on plugs is pretty low mileage for a modern engine. I hate just replacing stuff without some indication it might be the cause of the problem. The dealer replaced a coil 10K ago that had a crack in it but the engine management computer flagged it due to misfiring - the engine never actually felt like it was 'missing'. Usually the computer 'sees' misfiring long before I could find something like a crack so I'm not inclined to think that might be the issue. Usually mixture issues get flagged by the O2 sensors before they are detectable as a surging engine - at least in my experience. Anyone know if there is a way to monitor the signal the computer is sending to the throttle plate while underway? I'd like to see whether it's fluctuating in correlation to the engine surging.

  4. #4
    robertplattbell
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    Throttle?

    "Anyone know if there is a way to monitor the signal the computer is sending to the throttle plate while underway? I'd like to see whether it's fluctuating in correlation to the engine surging."

    Do these engines even have throttles? I thought the dual VANOS controlled the air intake, hence the fly-by-wire gas pedal.

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    Could be

    My old 750 developed a bad spot in the potentiometer, or foot pedal throttle thing, and I had to replace it. It was simply a dead spot. I don't know how it could cause a surge, but stranger things have happened.

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    It's not the engine...

    OK. I did a little more investigation. Turns out it's not the engine at all. It's the transmission. By putting the tranning in manual mode I have discovered that the problem occurs when the RPMs are between 1500 - 2000 and the transmission is in 5th gear. What happens is that it feels like the transmission disengages (loss of power to the wheels) for about half a second at intervals of about 20 seconds. The tach does not go up so the engine must still be loaded but there is clearly a feeling that power is lost to the wheels and then just as suddenly restored. Anyone have any ideas?

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    Re: It's not the engine...

    I have an 02 x5 4.4 with the same transmission hesitation. It started like you have described... where at 1500-2000 rpm the gauge will bob up and down and there will be little power. The problem will go away in full manual mode. The issue is that the bands that hold individual gears are going bad and the pressures that hold the gears in place are not holding. I am afraid my problem just gets worse and worse with time. I am going to change the transmission fluid, filter, gasket and try to nurse the transmission along for a little further... but will eventually need to be rebuilt/replaced. I will let you know if this helps with the problem. I have already replaced fuel filter, spark plugs, boots, oil, oil filter, valve cover gaskets, etc.

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    Re: It's not the engine...

    My 2001 4.4 X5 is doing the same.

    Odd question - does anyone know how to accelerate the degrading process so the transmission will have to be rebuilt/replaced sooner ?

    The method to my madness is that I've got 1 month left on my 3 month engine and gearbox warranty. Why not let the dealer take the hit if I can ?!

  9. #9
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    X5 hesitation in 5th gear

    Quote Originally Posted by studioj View Post
    OK. I did a little more investigation. Turns out it's not the engine at all. It's the transmission. By putting the tranning in manual mode I have discovered that the problem occurs when the RPMs are between 1500 - 2000 and the transmission is in 5th gear. What happens is that it feels like the transmission disengages (loss of power to the wheels) for about half a second at intervals of about 20 seconds. The tach does not go up so the engine must still be loaded but there is clearly a feeling that power is lost to the wheels and then just as suddenly restored. Anyone have any ideas?
    Could you tell how you resolved this issue? You have described identically what I am experienceing on 04 X5 4.4 - Thanks!
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    Same problem w/ my 4.4 x5

    My 05 X5 4.4 is having the exact same problem at 80k. I narrowed the issue down to 5th gear only by driving in manual mode or shifting to manual from auto or sport mode to see what gear it was in when cutting out; it also seems to go to 5th and run at low rpms even when going 35mph or so when in auto or sport mode. There were no fault codes showing when diagnosed, to trans failure indicator lights on dash and problems such as electric, tire pressure, fuel pump, trans fluid in need of flushing were all eliminated as causes. Software updates and computer resets all failed to resolve.
    Sorry for the bad news...but the problem has now been narrowed down to the transmision by the last 2 authorized BMW mechanics & 2 dealerships I've taken it to. I also spoke w/ ZD, the manufacture of this transmission and apparently the bushings in the trans. have been made, for the last 7 or so years, out of newer European regulated, environmentally compliant materials that have been seen to fail at as low as 50k.
    BMW speculated that a valve body replacement may solve the problem, however that was not guarenteed to resolve it, so a full trans replacement was recommended. ZD mentioned that even if the valve body only was bad, that I shouldn't expect to get many more miles out of the bushings, so a whole new trans was recommended by them as well.
    I called BMW usa to see if any recalls were in the works and they said no and provided no assistance. Very intermittent trans problems started within the warrenty period however were not accurately diagnosed till now.... so good luck as BMW doesn't seem willing to stand behind their product.
    ZD has authorized service centers in the US that do rebuilds for $3500-$3700 (not including, installation or shipping), so if you have a good transmission shop you'd probably be looking at a $5500(ish) repair. The BMW dealers have quoted me in the $8000-$9000 range for a remanufactured trans installed.
    Pretty shocking for a $70k car to have such issues at such low milage!! Pl
    Hope this helps.
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    RE: Same problem w/ my 4.4 x5

    amtash, that's a bummer about your BMW. Like seriously, for such an expensive car and at such low mileage. At this point I'd go searching for an auto repair shop that specializes in transmissions. Do lots and lots of shopping around with lots of research. A transmission overhaul is not something you want to do twice. At the same time, you already paid an arm and a leg and another leg for your BMW, so you don't want to pay the other arm for another transmission. Best of luck to you.
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