Bimmerfest - BMW Forums

Bimmerfest - BMW Forums (http://www.bimmerfest.com/forums/index.php)
-   X5 E70 (2007 - 2013) (http://www.bimmerfest.com/forums/forumdisplay.php?f=159)
-   -   *Video included* Weird behavior of '08 3.0si naturally aspirated engine (http://www.bimmerfest.com/forums/showthread.php?t=655077)

autoque 10-30-2012 02:31 PM

*Video included* Weird behavior of '08 3.0si naturally aspirated engine
 
http://youtu.be/2WHHdVWZUNE?hd=1

Only when the engine is warm does this happen. Around 00:16 seconds, you can see the rpm needle rise up a few hundred rpms only to go down again after a couple of seconds. It does this almost everytime when the engine is warm (usually when it had been used an hour or two before).

How about others with the 3.0si engine?

ard 11-06-2012 08:12 AM

i dont think there is anything 'wrong'... i suspect this may simply be a stack up of tolerances or a symptom more pronounced in your example.

But.... you should be able to get an explanation, right? If it is right or wrong, it is doing SOMETHING.

Look at this document: http://www.bmwmotorsports.org/pdf/e7...%20Engines.pdf

Page 25. Note how there are valves into the intake that involve the fuel tank and evap control...perhaps at start up you are getting something pressurizing in the first few moments of start up. DOES IT do it irrespectiev of how full the tank is?

Also, there is an idle air control something... at start up the DME controls air and fuel as the engine warms and stabilizes. Snoop around the directory for the website above, maybe you'll find something. There may not be a valve per se, but there is some way air is controlled at start.

look at this. page 6:

http://www.bmwmotorsports.org/pdf/e7...Management.pdf

Idle speed boost.

Hmmm....

autoque 11-06-2012 07:06 PM

Thanks ard. Idle speed boost. Hmmm.

I'll monitor the situation and see if it becomes worse or better.


All times are GMT -7. The time now is 02:53 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms