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      03-26-2018, 12:55 PM   #1
powaq
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Jumpy rpm on acceleration and decelleration

Hi guys,

I've been having this issue with some hesitation and a jumpy throttle on my N52 Coupé.
When I'm driving along and mash the accelerator to WOT my rpm dips slightly before taking off, and you can (although not every time) feel the car hesitating a little bit. The weird thing is that it does the same thing when coming off WOT.
I've had the issue for quite some time but it seems to be getting worse. Or it could be that I'm paying more attention to it..

Anybody has ideas? Clutch (it's a manual car)? engine mounts? diff (I have a Quaife LSD)? VANOS? Is it normal?

Last week I had a rough idle and weird throttle response (or lack thereof). I read my codes and I got a P1553 code, which is a VANOS code. So I took out the solenoids, cleaned them and put them back in (switching them as well). That fixed the rough idle. The car runs super smooth again and throttle response is fine again. Either way, the car was doing before and after cleaning those solenoids. So I'm not sure if it's even remotely related.

At the end of last year I had a coil go bad on cylinder 1, I replaced that one and I did all the plugs as well. So I doubt that's causing it. I have a backup coil because I accidentally ordered two so I could try and swap every coil to see if it helps..

I have uploaded a small videoclip which illustrates the issue. Not the best clip but my girlfriend had some issues keeping the phone stable at WOT .
But you can see what's happening.

So, any ideas as to what the issue could be?


Last edited by powaq; 03-26-2018 at 12:58 PM.. Reason: fixed youtube link
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      03-26-2018, 01:21 PM   #2
pokeybritches
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How old are your battery and alternator?
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      03-26-2018, 02:53 PM   #3
powaq
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I honestly wouldn't know. The alternator is, as far as I know, as old as the car (any way to check?). Battery is at least 1,5 years old (I've owned the car since September 2016). I could ask the previous owner. I tried to check the date on it a few weeks ago when I had a flat battery but couldn't find a date stamp.

EDIT: found the date stamp on the battery: Week 41 (October) of 2015. So no, not that old

Last edited by powaq; 03-27-2018 at 07:33 AM.. Reason: added information
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      03-27-2018, 10:10 PM   #4
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As Josh said, I'd be checking the Batt and alt first.
See if you can swap the Batt out with a know good unit and go from there.
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      03-28-2018, 07:30 AM   #5
powaq
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Thanks. I'm just wondering: how and why would the battery and/or alternator cause behavior like that?

I'm avoiding to just throw parts at the issue..
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