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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 12-01-2013, 09:24 AM   #1
salahy
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very weird issue with the rpm

hi guys, I am having weird issue while moving the steering or lighting the headlights or even closing and opening the windows,
whenever I don anyone on Idle (N) the rpm jumps and goes back.

what does that mean ? could it be a belt or the pulley or the idler ??

Thanks

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Last edited by salahy; 12-02-2013 at 01:43 AM.
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Old 12-01-2013, 12:31 PM   #2
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very weird issue with the rpm

Could mean you need a new battery or your alternator is weak
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Old 12-01-2013, 12:39 PM   #3
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very weird issue with the rpm

Quote:
Originally Posted by salahy View Post
hi guys, I am having weird issue while moving the steering or lighting the headlights or even closing and opening the windows,
whenever I don anyone on Idle (N) the rpm jumps and goes back.

what does that mean ? could it be a belt or the pulley or the idler ??

Thanks
Do you mean it drops and then comes back up? If it moves about 50 RPM that is normal. When in neutral the engine is not under much load and when you suddenly load the engine either via the power steering pump when turning the wheel or via the alternator when turning on high power accessories the engine RPM will drop and it will take a half second for the computer to compensate via the idle control valve on non drive by wire engines or via the throttle body on drive by wire engines. When you are in gear there is already a load on the engine and the load from the power steering or alternator is minor and hardly noticed by the engine.


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Old 12-02-2013, 01:43 AM   #4
salahy
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Thanks guys for your answers, I added a video if this could help
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Old 12-02-2013, 02:29 AM   #5
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Normal. Listen to scott.
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Old 12-02-2013, 05:50 AM   #6
Chadsere
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very weird issue with the rpm

If the engine shakes when the idle speed drops, that isn't normal. Does the engine sputter at all?


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Old 12-02-2013, 06:02 AM   #7
salahy
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If the engine shakes when the idle speed drops, that isn't normal. Does the engine sputter at all?


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no It doesn't sputter but the car shakes a little when the rpm changes
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Old 12-02-2013, 06:09 AM   #8
Chadsere
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very weird issue with the rpm

I actually have the same problem. Wasn't the DISA, Idle Control Valve or the Throttle Body. Could be a fuel filter or vacuum leak. As a temporary fix if the shaking really bothers you, you can overtighten your throttle cable to increase RPMs. That's what I did. It doesn't fix the problem, just masks it


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Old 12-10-2013, 11:46 AM   #9
salahy
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thanks but I guess this happen when the car is cold, I have this problem now when I put the car or reverse
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Old 12-10-2013, 11:51 AM   #10
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Originally Posted by salahy View Post
no It doesn't sputter but the car shakes a little when the rpm changes
IT'S NOT A PROBLEM.

Stop worrying about this. You put a new load on the engine that slows it down, the computer sees that the engine slows down so it makes an adjustment to bring the speed back up. This is all perfectly normal. The thing that's not normal is that you even notice that it is happening.
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Old 12-10-2013, 12:12 PM   #11
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The "problem" itself is "normal" but idle dip seems to be exacerbated further by a weak idle control system.

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Old 12-10-2013, 12:36 PM   #12
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I've experienced things similar to this, usually in drive not neutral. And especially when turning the wheel, in fact the the two years I've had the car I've had it randomly stall four times. I've cleaned TB, ICV, replaced boots, DISA o ring, next thing to look at is vaccum leak possibilities. I'd suggest the same to you if it bothers you that much.
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