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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

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 02-18-2014, 03:05 PM
spong007 spong007 is offline
525i
Location: staffordshire
 
Join Date: Feb 2013
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Mein Auto: bmw 5series 525i
why why why

can any one help me when i disconnect the air mass sensor my car seems to run better and with more power why would this happen. because i dnt want to leave it unplugged as i like to have all wires in the right places as that's how problems start well that's what i've been told
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  #2  
Old 02-18-2014, 03:41 PM
Flightmedic Flightmedic is offline
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Mein Auto: 525i
Usually it means the computer reverts to a baseline setting and uses preprogrammed safe factors to run on. Certainly the CEL is on.
As always, check mechanicals first. In this case look at all of your boots and hoses, to include hidden little vacuum hoses. I didnt catch your model there, but look at PCV hoses (some run to dipstick tube)
Little bellows like to crack. Buy two of them so you have on the shelf.
I keep a cheap Code reader to reset the CEL. Only replace MAF after assuring all vacuum leaks are fixed. I would even clean the MAF first.


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  #3  
Old 02-18-2014, 05:26 PM
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matt540 matt540 is online now
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why why why

If you have the bentley manuals and a multimeter you can test your MAF to see if that is the problem. Having extra vacuum hoses is also a good idea.


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  #4  
Old 02-18-2014, 06:04 PM
JimLev JimLev is offline
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Probably runs better because your MAF is starting to fail. Usually when the DME reverts to the preprogrammed values it doesn't run quite as well and will have less power.
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  #5  
Old 02-18-2014, 06:12 PM
Flightmedic Flightmedic is offline
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Location: Mohave Desert
 
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Mein Auto: 525i
Always check mechanicals first. Unmetered air will cause poor running and incorrect airflow values. Unplugging the MAF in the case of an air leak will totally remove an incorrect value and cause improved running. If you have a Bently manual, by all means measure values.
You know how the Dr does a head to toe exam no matter what you visit for? Do that for your Baby.


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  #6  
Old 02-18-2014, 07:38 PM
Burning2nd Burning2nd is offline
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test test test...
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  #7  
Old 02-19-2014, 06:44 AM
spong007 spong007 is offline
525i
Location: staffordshire
 
Join Date: Feb 2013
Posts: 11
Mein Auto: bmw 5series 525i
thanks for all the information been on it all day an found a crack in one of the air pipes goin at weekend and will get the code reset after fitting part sorry didnt say what car i ad 525i auto 01 plate thanks again
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  #8  
Old 02-19-2014, 06:47 AM
spong007 spong007 is offline
525i
Location: staffordshire
 
Join Date: Feb 2013
Posts: 11
Mein Auto: bmw 5series 525i
Quote:
Originally Posted by Flightmedic View Post
Usually it means the computer reverts to a baseline setting and uses preprogrammed safe factors to run on. Certainly the CEL is on.
As always, check mechanicals first. In this case look at all of your boots and hoses, to include hidden little vacuum hoses. I didnt catch your model there, but look at PCV hoses (some run to dipstick tube)
Little bellows like to crack. Buy two of them so you have on the shelf.
I keep a cheap Code reader to reset the CEL. Only replace MAF after assuring all vacuum leaks are fixed. I would even clean the MAF first.


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thanks for info found a small crack in air pipe soory i didnt say what i drive its a 525i auto 01 plate thanks again
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  #9  
Old 02-19-2014, 06:55 AM
Cabover1000 Cabover1000 is online now
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Location: Belding,Michigan
 
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Mein Auto: 1999 bmw 528i
Can someone post the procedure to test the maf. That would be great.
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  #10  
Old 02-19-2014, 12:23 PM
Flightmedic Flightmedic is offline
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That elbow at the Throttle body cracks at the small boot. While there, find that little tiny vac hose under the back of the manifold that supplies the EGR valve, note the direction of the check valve and replace that.
Also, while the air box and boots are off, follow the dipstick tube down, find the rubber hose on the "Y" above that and replace that hose.
You should be about $45 total, plus a quality beer.
Also, its time to do a repair kit on the DISA valve. (the black box on the manifold) Research that too, easy fix but makes huge difference.
Buying a $59 code reader to keep in the car will make your life easier....


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  #11  
Old 02-19-2014, 12:39 PM
edjack edjack is offline
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Quote:
Originally Posted by Flightmedic View Post
That elbow at the Throttle body cracks at the small boot. While there, find that little tiny vac hose under the back of the manifold that supplies the EGR valve, note the direction of the check valve and replace that.
Also, while the air box and boots are off, follow the dipstick tube down, find the rubber hose on the "Y" above that and replace that hose.
You should be about $45 total, plus a quality beer.
Also, its time to do a repair kit on the DISA valve. (the black box on the manifold) Research that too, easy fix but makes huge difference.
Buying a $59 code reader to keep in the car will make your life easier....


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Do they have OBD-II in Europe, with the dashboard connector?
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  #12  
Old 02-19-2014, 12:44 PM
jygesq jygesq is offline
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if it runs better disconected usually means it is bad

Quote:
Originally Posted by spong007 View Post
can any one help me when i disconnect the air mass sensor my car seems to run better and with more power why would this happen. because i dnt want to leave it unplugged as i like to have all wires in the right places as that's how problems start well that's what i've been told
buy a new one
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  #13  
Old 02-19-2014, 01:46 PM
tcbDE tcbDE is offline
Registered User
Location: Aachen, Germany
 
Join Date: Mar 2013
Posts: 97
Mein Auto: (E39) 2001 530iA M Sport
Quote:
Originally Posted by edjack View Post
Do they have OBD-II in Europe, with the dashboard connector?
Yes. Why do you ask?
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