05-29-2015, 11:07 AM | #1 |
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M4 pulsing/shaking under load
Looking for some help here. My car is a Feb '15 build with about 1900 miles currently. I'm experiencing what I can best describe as a rapid pulsing or shaking sensation in the car around 60mph, most notably doing a 3rd gear pull around 4500rpm and a 4th gear pull around 3500 rpm. I never feel it in 1st or 2nd - presumably because I don't reach 60mph in those gears. The shaking can also be felt when maintaining 60(ish)mph in any gear, but it's much more pronounced under heavy acceleration. The obvious answer is tire balance but I eliminated that variable today through road force balancing all 4 corners. Granted, the left rear was out of spec but the issue still exists. I do have spacers and lowering springs but they have been on the car since the day 3 of ownership and this issue didn't begin until a few weeks ago. Also of interest is the problem is worsened when I activate my JB4 (Map 1). The pulsing sensation is still present in the same scenarios with the JB4 off (Map 0), but not as noticeable.
The tach doesn't drop when the pulsing occurs and the car pulls strong...but I have to think something isn't normal. I should also add this isn't the shaking sensation one gets when trying to accelerate in too high a gear as I've experienced that too. Anyhow, I wanted to solicit some feedback from you good folks before I removed the JB4 and made a service appointment. Thanks in advance- |
05-30-2015, 02:09 AM | #2 |
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Any Drivetrain Malfunction warning lights?
Where do you feel the pulsing? Is it felt in the steering wheel / lower floorboard or pedals? Does it occur in a "rhythmic" interval? This usually means you have a bent rim/tie-rod/strut/suspension item. This usually becomes apparent when you're going 60-80mph. You'll hear and feel a thumping. You may notice the steering wheel shaking if you take your hands off it. Usually more prominent when you're cruising along and the car is not under load. Engine related = You floor it and the car goes, but acceleration is very choppy. It feels as if the car is about to stall, but then accelerates again, but then feels as if its going to stall. This cycle repeats at half second intervals until you let off the gas. Can also be described as hesitation. Based on what you've described it seems as if you have an engine related issue. I'd check and make sure all connectors and hoses are in place under the hood. It appears as if your car is starting to misfire which means you may have a coil/injector/spark plug that's about to fail. |
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05-30-2015, 05:13 AM | #3 |
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I have noticed the same in my M4. My car shakes sometimes a little bit when stationary or waiting at a red lights for example. I dont know what it is. The tach also doesn't move. My dealer hooked it up at the computer but nothing, no errors. Its not that bad. If it gets worse I'll let them check it again.
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05-30-2015, 08:18 AM | #4 | |
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Again, no perception of engine stall but the fact that the JB4 magnified the issue makes me think it's engine/turbo related as you suggested. Oh, and no malfunction lights to date. |
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05-30-2015, 08:22 AM | #5 | |
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05-30-2015, 09:36 AM | #7 | |
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How large are your spacers? If you really want to root cause it, take the car back to stock and go from there. Although since you modded almost immediately after buying, you will probably need someone with a frame of reference for what "normal" actually is. |
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05-30-2015, 10:02 AM | #8 |
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When you balanced wheel/tire are the spacers included?
Never had spacers so no clue how they are installed. Shaking at a certain speed is almost always an imbalance of the wheels. |
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05-30-2015, 01:13 PM | #9 |
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Everything is fine under load. Only stationary from time to time. Car is 100% stock with MPE. Drives fine. Maybe bad gas.
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07-05-2015, 11:26 PM | #10 | |
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07-06-2015, 06:37 AM | #12 |
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Really hard to diagnose this over the internet, and you really need to take it to the dealer.
It is unlikely to be wheel / tire / brake related if it only does this under load. Could well be a driveshaft problem. The first sign of a driveshaft problem is usually a pulsation or slapping sensation under heavy load or acceleration. There are luterally hundreds of things that could do this though. Could conceivably be engine / drivetrain / suspension related. |
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07-06-2015, 08:11 AM | #13 | |
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07-06-2015, 08:19 AM | #14 |
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Sorry I never updated the thread. I did take my car to the dealer and rode with the shop foreman. I was easily able to replicate the problem and he consented to open a PUMA case. A week later the BMW regional technical engineer was at the dealership so I returned the car for the two of them to take a drive. I wasn't able to ride or stay due to my schedule, but I'm told by my SA that he was "almost immediately" able to identify the pulsation as the new "M-differential operation under heavy acceleration...which is operating as designed". In other words normal behavior. I questioned the verdict because of the lack of initial response to this thread but I felt somewhat relieved that at least my problem/concern was now documented in case a issue does occur in the future.
As an aside, my SA specifically asked if my lowering springs or wheel spacers would in any form contribute to the issue and the RTE said no. |
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07-06-2015, 08:27 AM | #15 | |
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thanks for the pep talk "dad"
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07-06-2015, 08:32 AM | #16 | |
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07-06-2015, 10:13 AM | #17 |
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Did you have your JB4 hooked up when you were at the dealership? Did the RTE comment on it if so?
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07-06-2015, 11:19 AM | #18 | |
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07-07-2015, 02:56 PM | #19 | ||
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04-06-2017, 03:45 PM | #20 | |
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10-17-2019, 09:58 PM | #21 | |
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Doug, and the other more mature posters, I seem to have a similar problem, especially when I have the car in the M2 setting and under heavy acceleration. Would love to know if anyone has more updated info or feedback. Thanks, mates. |
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10-18-2019, 09:49 AM | #22 |
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I have EXACTLY the same problem, SAME symptoms as described in your post. Did some digging around, and it seems like the 2015's suffer from the rear differential bushings coming loose (<---insert correct term here). Took it to the dealership, they assured me that the bushing is not the reason but couldn't tell me what it was. I have experience this both with stock 19" wheels and tires and it feels the same with the 20" wheels I currently have on the car.
I agree it's a "bad" feeling when the car does this but doesn't seem anything major from what I have gathered, at least, thus far! |
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