01-20-2025, 02:45 PM | #1 |
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Wobble at idle ... normal? 640d
Hi all,
I’m 2 months into ownership of a lovely blue 2017 year 640d Gran Coupe. No mods, just factory standard. I’ve noticed that at idle, the idle needle jitters ever so slightly. By literally a millimetre at the ideal rev point. This is also accompanied by a very slight wobble. It’s a very slight sensation of side to side wobble coming from the engine into the cabin. Just wondered if this is normal or something more sinister. Any advice would be welcome. |
01-21-2025, 07:40 AM | #2 |
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hi,
i also have a 2017 640d..this is my third 640d. it is normal for the rev counter needle to bounce ever so slightly when idling from cold until it gets to normal operating temperature then it should be steady. all mine have idled when warm at just under 700rpm..the top of the needle sits just under the 700 line. the slightly fluctuating revs is more noticable in winter as it takes longer for the car to get to normal operating temperature...which is when the temp guage needle is straight up at 12 oclock...also the temp guage is oil temp,not coolant temp. however i dont feel any wobble or vibration in the car itself,and the rev counter needle fluctuates maybe half the thickness of the needle.. the only other thing that might cause fluctuation,only when cold,would be glow plug/plugs failing,but you would likely see smoke from the exhaust for the first 5 or 10 seconds.a decent fault code reader would show if a glow plug was failing. |
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Dpfghela17.00 |
01-21-2025, 08:37 AM | #3 |
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Glad it isn't just me then! I could swear I felt the same exact feeling a couple of weeks ago when I started the engine from cold.
It doesn't happen every time, probably 1 out of every 10 cold starts. At first I thought it was a stretched chain but this would happen constantly? However, at this age of vehicle I would think it could be put down to Engine Mounts which for age/mileage may need changing. It's like a really strange shimmy within the cabin just after the car starts. |
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Dpfghela17.00 |
01-22-2025, 04:57 PM | #5 |
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Thanks all for those really comprehensive comments!!
On mine, the shimmy is pretty constant. It’s not intrusive but noticeable. Will get a check of the engine mounts carried out. |
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01-23-2025, 07:13 AM | #6 |
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to original poster...if your shimmy is constant ,meaning hot or cold engine then its not likely glow plugs for you...it could be engine mounts.but it also sounds like rough engine running,like the ecu is constantly trying to trim the engine fuel to get optimum running..i had a similar issue when i had a slight air leak on the inlet manifold...the intake air (maf) sensor sensed the amount of air coming in and this set the fuelling by the ecu,but due to the air leak sucking more air in at the manifold ,the o2 sensor had a diferent reading in the exhaust than expected so the ecu was constantly trying to adjust the fuel mixture as the maf sensor and o2 sensor were out of sync due to extra air from the inlet manifold leak...similar shimmy due to rough running could be dirty or malfunctioning sensors.maf,map,even air temp sensors.or any air/vacuum leak..
if engine mounts are worn this can usually be noticed with the engine running at idle,car stationary and you moving the gear shifter from reverse to forward and back again. in approx 200k miles in bmws iv never had an engine mount go sloppy,but some people on here have...iv also seen on forums that non genuine engine mounts dont always solve the problem where genuine bmw mounts usually do. have you had a decent code reader on your car? it might pick up some rough idle fault codes. good luck. |
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Dpfghela17.00 |
01-23-2025, 06:02 PM | #7 | |
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Thank you for this. I’m intending to run it to my local BMW garage. They’ve done stellar work in the past and I want to keep the car as tiptop as I can. I’ll suggest some of those points and see what they pick up. Went back and checked the idle. It’s 700rpm with a very small 1mm dip as the engine turns over. Many thanks once again. Fingers cross they’re able to fix it! |
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