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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 02-27-2013, 03:40 PM
SeanMH-6 SeanMH-6 is offline
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Location: Clarksville TN
 
Join Date: Nov 2012
Posts: 115
Mein Auto: 2002 525i sport, premium
mild RPM pulsing at idle/voltage fluctuation

I have a mild pulsing RPM at idle regardless of engine temperature. fluctuates about 200rpm in each direction, maybe a bit less. symptoms are:

-fluctuates about 200 rpm at idle.
-EDIT all lights pulse in cabin.
-voltage fluctuates from 12.4V to 14V @ idle (test #9 OBC),EDIT: I CAN put a correlation together with the voltage and the RPM. just replaced alternator with a duralast.

My first thought is the duralast alternator is causing the voltage fluctuation which in turn is causing the weird idle. voltage also fluctuates while driving as well, but that is normal right?

Im getting Secondary air injection system insufficient flow on both banks. possibly a vacuum leak?

Last edited by SeanMH-6; 03-02-2013 at 06:26 AM.
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  #2  
Old 03-02-2013, 11:31 AM
SeanMH-6 SeanMH-6 is offline
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Location: Clarksville TN
 
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Mein Auto: 2002 525i sport, premium
SOLUTION: poor conductivity on duralast washer provided. Took it out of the mix and all seems well, constant 14 volts or higher.
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Old 03-02-2013, 11:36 AM
Bennt771 Bennt771 is offline
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Mein Auto: 2000 540i,89 Por 930,Vett
Wow, nice catch.
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Old 03-02-2013, 01:40 PM
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Fudman Fudman is offline
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Mein Auto: '02 530i Sport auto
Quote:
Originally Posted by SeanMH-6 View Post
Im getting Secondary air injection system insufficient flow on both banks. possibly a vacuum leak?
This could be a loss of vacuum (which activates the check valve), a stuck check valve or a failed pump. Open the hood and listen for the pump activation on a COLD startup. It should shut off after 60-90 seconds. If you don't hear it, then the pump has died and must be replaced. If it kicks on and shuts off, the problem is with the valve. Check the vacuum hose leading to the valve. It tends to crack due to the constant exposure to the exhaust manifold heat. The valve is constantly exposed to the exhaust stream and it will occasionally get stuck due to carbon deposits. It can be cleaned but it is easier to replace. Normal SOP is to replace the valve whenever the pump is being replaced.
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Old 03-02-2013, 02:04 PM
SeanMH-6 SeanMH-6 is offline
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Mein Auto: 2002 525i sport, premium
Thanks for the direction fudman. I have been diagnosing little by little. I checked the air pump valve to make sure it wasn't blowing exhaust into the pump. The pump is blowing steady too. The air pump valve on is going to have to wait until I have time to check them. You are referring to the air pump valve as the common failure right? Or are you referring to the electric valve or non return valve?
http://www.bimmernut.com/forum/5-ser...-e39-528i.html
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