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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 04-02-2011, 08:47 AM
VitaminXX VitaminXX is offline
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How the DISA Works

In this thread I doubt my DISA valve is malfunction. And after reading tons of threads about DISA, there are some thing I am not still clear. For example, from the documents Bluebee provided, the DISA valve should close when RPM is below 3750 and stay open when it is over this RPM. I am not sure if this is correct or not. So, I decided to hook up my computer to check the DISA activation status when driving on the road. Now I think I know how the DISA valve works.
http://www.bimmerfest.com/forums/sho...689&highlight=

The DISA valve is always open,not active, in any RPM unless you step on the gas pedal a little harder when accelerating. I am not native and it is hard for me to describe precisely without pictures. So, I am going to show you what I observed from my computer.

Idling: The DISA is "Not Active" means DISA is open



Step on the gas pedal: (A little bit hard and the DISA turns to "Active"



Release the pedal (The RPM is around 1300 and the DISA is "Not Active")


Step on the pedal but not so hard, the DISA remains at "Not Active"





Step on the pedal harder. (The DISA changes to "Active")





Release the pedal and cruising. (DISA opens again)





These are all my observation from DIS. My engine is M54 and DME is M43***12290;Other version may different.

Does anyone know why making longer intake path (DISA close or active) increase torque?
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  #2  
Old 04-02-2011, 08:58 AM
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champaign777 champaign777 is offline
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this is very insteresting thread bro
what was the engine RPM which triggered DISA to activate ?
BMW said around 4000 RMP :

below ~ 4000 RPM closed
above ~ 4000 RPM open
rest position, i.e. when removed - flap open

and why you dont fix your LCM/GM module ??? i guess you installed some new headlights no ?

Last edited by champaign777; 04-02-2011 at 09:07 AM.
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  #3  
Old 04-03-2011, 03:34 AM
VitaminXX VitaminXX is offline
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For M54 MS43 Engine, an BMW internal document says, below 3750rpm, the DISA is closed to increase air velocity to enhance torque at low RPM. So, I thought it is always closed as the RPM is lower than 3750. However, from what DIS shows me, the DISA is not always closed even the RPM is lower than 3750. It is activated, closed, when you step on your gas pedal a little bit harder when the RPM is lower than 3750. In this test, I also kicked down to raise the RPM over 5000 see if the DISA is activated. I did not see it is activated.


Regarding to LCM module error, it is because of engine oil level sensor. I am not in rush to replace it.

Quote:
Originally Posted by champaign777 View Post
this is very insteresting thread bro
what was the engine RPM which triggered DISA to activate ?
BMW said around 4000 RMP :

below ~ 4000 RPM closed
above ~ 4000 RPM open
rest position, i.e. when removed - flap open

and why you dont fix your LCM/GM module ??? i guess you installed some new headlights no ?
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  #4  
Old 04-03-2011, 08:16 AM
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champaign777 champaign777 is offline
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i will check my E39 525i with DIS and let you know
can you , please, print data for the rest of checks which you did ?
another question - can we check CCV aka oil separator like you did for DISA ? i dont think so ...

not sure that engine oil level sensor has no relation to LCM
you may to decode your LCM module in Progman

similar to this , page #26

http://forums.bimmerforums.com/forum....php?t=1567928

Last edited by champaign777; 04-03-2011 at 09:10 AM.
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  #5  
Old 04-03-2011, 08:54 AM
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Very interesting. Keep up the investigation! (Especially if the white dot moves with the DISA opening or not!).

I'll add this one to the list of links for how the DISA works (it still confuses the heck out'ta me as to how to test it since I don't have the software here).

- DISA VALVE FLAP BREAKS: the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) or the disa valve o-ring fails (1) (2) & how it can cause all sorts of cold-engine idle problems (1) & where to get just the DISA valve o-ring (1) & how the DISA valve operates (0) (1) (2) (3) & an example of how a broken DISA valve can ruin your engine (1) & how to test DISA operation (1) (2) (3) or temporarily repair your DISA valve with glue (1).


Last edited by bluebee; 04-03-2011 at 08:56 AM.
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  #6  
Old 04-03-2011, 04:54 PM
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it looks like your DISA is not working properly

I succeed to activate it on a very short time above 4000 RMP ( cant catch it even but i did it stationary and not on the road )

Cant activate it before 4000 RPM

I maybe do it again on the road sometime








Last edited by champaign777; 04-03-2011 at 05:01 PM.
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  #7  
Old 04-03-2011, 06:47 PM
VitaminXX VitaminXX is offline
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I will do a road test again to see if the DISA will be activated over 4000RPM today. I am collecting my old DISA data before I put new DISA in.

For LCM, below is what DIS detects and tells me.
I have three errors,
1. Light Check module lcm
2. Trailer module lcm
3. Check control message (LCM) lcm


1. Enter the LCM module.
LCM module not just control light function but also check controls. Enter the the light function and read the fault code, none. select "Check control"


2. Select "Check control"


3. Choose "Expert mode"


4. Read fault code. It shows thermal oil-level sensor


If you want to capture you laptop screen, I would suggest you to install a software "Autoscreenshot" which can capture your screen every 1, 2, 3..... sec whatever you want.

Quote:
Originally Posted by champaign777 View Post
it looks like your DISA is not working properly

I succeed to activate it on a very short time above 4000 RMP ( cant catch it even but i did it stationary and not on the road )

Cant activate it before 4000 RPM

I maybe do it again on the road sometime







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  #8  
Old 04-03-2011, 07:43 PM
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champaign777 champaign777 is offline
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thanks for tip
expert mode just read your errors
i doubt that oil sensor has something to do with your LCM
just decode it and see what's happening

Last edited by champaign777; 04-03-2011 at 08:26 PM.
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  #9  
Old 04-03-2011, 08:05 PM
VitaminXX VitaminXX is offline
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But my headlight is halogen but not Xenon, and I did not change my headlight. Do you still sugget to decode my LCM?
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  #10  
Old 04-03-2011, 08:15 PM
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how it started ?
maybe dealer did some update on this car ?
Some people said LCM module throw errors in case of software mismatch ... this may explain your oil sensor error

nothing will happen if you will decode it
when i tested some software i decoded my LCM module 3 times
better to do it in progman ( more clean ) and then clean errors in DIS
progman is smart , if needed it will decode GM as well and if decode is not possible due to more new software update will fail

Last edited by champaign777; 04-03-2011 at 08:24 PM.
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  #11  
Old 04-05-2011, 07:14 AM
VitaminXX VitaminXX is offline
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I do not have Xenon light and in SSS, should I follow up the post to add Xenon for decoding?
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  #12  
Old 04-05-2011, 07:21 AM
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No, Don't add Xenon to a non-xenon car! The software is awfully buggy but I think the oil sensor is the problem here...

Re-flashing modules takes off their lifespan. The memory can only be reliabliy written to a certain number of times (10-20 IIRC) before it starts erroring. Better to clear codes with INPA if you've got that.
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Last edited by bmw_n00b13; 04-05-2011 at 07:22 AM.
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  #13  
Old 09-26-2011, 01:02 PM
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For the record, a user recently had cause to remove the flap in the DISA valve and is testing how the engine runs sans an operative DISA:
- Bingo!! I may have solved the misfire and lean codes P0171, P0174, P0300



See also:
- Why check the DISA at 85K miles to 90K miles or whenever the airbox is removed (1) (2) & how to repair a rattling DISA unit (1) (2) (3) & why the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) & how the disa valve o-ring fails (1) (2) & how it can cause all sorts of cold-engine rough idle problems (1) (2) & where to get just the DISA valve o-ring (1) & how the DISA valve operates (0) (1) (2) (3) (4) & an example of how a broken DISA valve can ruin your engine (1) & how to test DISA operation (1) (2) (3) (4).
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  #14  
Old 10-10-2011, 09:51 AM
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For the record, we need clarification on WHERE the DISA gets its vacuum from and how it operates with it.
- How to test DISA operation (1) (2) (3) (4)

For example, when I removed mine to perform a visual inspection last week, I was surprised there were no vacuum hoses attached:


Apparently, the 'vacuum' comes from the manifold itself, through a tiny filtered hole:

NOTE: Vacuum apparently comes in from this filtered hole shown below ... (ignore the caption as the picture is re-used and the question was confirmed in that thread).

This thread contains some information about the vaccum, but, still it isn't crystal clear 'how' it works:
- E39 (1997 - 2003) > DISA Autopsy

Quote:
Originally Posted by pshovest View Post
This is wrong.
The DISA flapper is either fully open or fully closed. There is no intermediate position on a properly working DISA valve. A DME controlled solenoid uses manifold vacuum to close DISA flapper and spring action to open the DISA flapper.

Paul S
BMW CCA 69606
Quote:
Originally Posted by AnotherGeezer View Post
I stand corrected Paul. My vacuum secondary comparison was also off. After much research I found this to be the best DISA operation decription I could find.

"The disa valve has an outer seal (inside the manifold) and a diaphragm inside the valve itself. The valve is constantly fed 12 volts during normal throttle operation and then open circuits on higher RPM and throttle opening. This deenergises the coil which stops the manifold vacuum from reaching the diaphragm. The butterfly then springs open."

Do you concur?

Last edited by bluebee; 10-10-2011 at 09:54 AM.
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  #15  
Old 10-10-2011, 10:13 AM
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What I did find interesting is that even though my DISA valve was "unflapping " it threw no codes. I'm pretty sure I had a slight vacuum leak due to the total loss of spring tension or resistance to the flapper moving therefore no intake seal but the car never let me know. Also, upon further inspection, the pin at the distal portion of the DISA was easily removed by simply giving it a slight tug. Glad I caught this little defect before a piston did.
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Old 10-14-2011, 01:36 AM
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Quote:
Originally Posted by AnotherGeezer View Post
I'm pretty sure I had a slight vacuum leak
There is something decidedly non obvious about how the "vacuum accumulator" works in the DISA.
- Strange results from a simple test of the M54 DISA valve today



For example, this PDF from RDL purports to explain how the DISA operates:
- m54x5[1].pdf (see pages 42 to 44)

Here is an excerpt from that PDF; the red italics are mine; the rest is verbatim (notice the use of the vacuum accumulator):

Quote:
The resonance system provides increased engine torque at low RPM, as well as additional power at high RPM. Both of these features are obtained by using a resonance flap (in the intake manifold) controlled by the ECM.

During the low to mid range rpm, the resonance flap is closed (i.e., the flap is actuated by alternator voltage such that it is held vertically against spring tension). This produces a long/single intake tube for velocity, which increases engine torque.

During mid range to high rpm, the resonance flap is open (i.e, the control voltage is reduced to zero which causes the flap to return to the horizontal rest position due to spring tension) . This allows the intake air to pull through both resonance tubes, providing the air volume necessary for additional power at the upper RPM range.

When the flap is closed, this creates another "dynamic" effect. For example, as the intake air is flowing into cylinder #1, the intake valves will close. This creates a "roadblock" for the in rushing air. The air flow will stop and expand back (resonance wave back pulse) with the in rushing air to cylinder #5. The resonance "wave", along with the intake velocity, enhances cylinder filling.

The ECM controls a (magnetic) solenoid valve for resonance flap activation. At speeds below 3750 RPM, the solenoid valve is energized (with alternator voltage at the harness connector) and vacuum supplied from an accumulator closes the resonance flap (where the vacuum accumulator is apparently a one-way flap valve with a 1/16" entrance hole in the side of the DISA) . This channels the intake air through one resonance tube, but increases the intake velocity.

When the engine speed is greater than 4100 RPM (which varies slightly - temperature influenced), the solenoid is de-energized (i.e., the harness control signal goes from ~13.8 volts DC to zero volts DC) The resonance flap is sprung open (by spring tension), allowing flow through both resonance tubes, increasing volume.
With regard to vacuum, I wonder why BOTH the 12 volt magnetic solenoid AND a one-way check valve vacuum accumulator is needed simply to close the flap?

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Old 10-14-2011, 10:58 AM
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For the record, how the DISA valve actually (mechanically) operates was not apparently known to any of us, until now ...

Here's the best guess we have, so far:
- Strange results from a simple test of the M54 DISA valve today

Quote:
Originally Posted by seemyad View Post
You hit the nail on the head Blubee.

The diaphragm (when vacuum is applied) and the spring are two opposing forces on the flap. The spring is why the flap is open when you hold the DISA in your hand.

From the videos I linked in a previous post (above) I can see the spring tension on the flap when the guy is forcing the flap closed. He then closes the flap by hand and puts his finger over a small hole where the diaphragm is located. The vacuum seal he creates with his finger forces the flap to remain closed against the tension of the spring.

The electrical portion merely creates/completes the path for the vacuum giving the diaphragm enough "suction" to force the flap close (opposing the spring tension). When you exceed X RPM the 12 VDC is removed thereby opening an "escape root" for the vacuum (basically allowing air into the diaphragm). The tension from the spring then forces the flap open.

When the RPM drops back below the threshold, the 12 VDC is reapplied to the solenoid which then closes the path to allow a vacuum to form again which forces the diaphragm to close the flap.

"As soon as the solenoid valve switches (on dropping below the switching speed) the vacuum reservoir and vacuum unit..." (I believe the vacuum unit to be where the spring and diaphragm are located) "...are reconnected and the connecting flap closed." NOTE: As I have not held a DISA in my hand yet I am unsure as to the location of the "vacuum reservoir".

There is much more to the DISA than meets the eye. Although the parts that comprise the DISA are not expensive individually, I can better appreciate the cost. The reality is it is amazing that so many plastic moving parts and the rubber diaphragm hold up as long as they do under such extreme pressure, vibration, and temperature variations (below freezing to above boiling point of H2O).

I no longer view the DISA as an overpriced cheap piece of plastic. It's moving parts appear to last over ten years and over 100,000 miles under extreme; pressure, vibrations, and temperature variation. The DISA alone is engineered better than most American cars (sad fact).

Also, normal rubber would dry up and crack within a year under these conditions yet the diaphragm retains its properties for a decade or more (hot or cold).



Blubee, there IS value in your desire to understand how stuff works. Thank you for always going that extra mile.

You gave me the missing clue when you mentioned the "magnetic switch". I have an extensive electronics background (which paid for my BMW) so that is all I needed to put the rest of the puzzle together. That's what I call "team work".


.
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  #18  
Old 10-14-2011, 12:10 PM
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seemyad seemyad is offline
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Quote:
Originally Posted by VitaminXX View Post

These are all my observation from DIS. My engine is M54 and DME is M43***12290;Other version may different.

Does anyone know why making longer intake path (DISA close or active) increase torque?
GREAT POST! Thank you for the screen shots!

As to your question concerning torque:


PART 1:

Envision a long pipe (intake manifold). As piston #1 is forced down via the fuel/air igniting, a trap door opens and air is forcibly sucked into the piston at an incredible velocity through this long pipe. When the piston reaches it's lowest point the trap door closes yet the air has all of this velocity and no where to go which causes a "back wash/wave" of air pressure from the dead end that previously led to piston #1.

This back draft (extreme pressure due to the long narrow pipe) forces air into the path of least resistance which will be the piston that just began its journey down after it's fuel/air mixture ignites (lets say #5). The back draft pressure forces additional air into that piston giving more bang to the fuel/air mixture as more oxygen is more volatile and will burn hotter than less oxygen. The (ratio) diameter of the pipe is increases by shortening or lengthening the pipe itself. Example, turn on a water hose. Watch the water pour out and fall directly to the ground. Now use your thumb to close half of the opening (which is cutting the diameter in half) and watch the ensuing pressure force the water into one direction AGAINST the force of gravity. You did NOT create more pressure by turning on more water. You DID create more pressure by narrowing the passageway for the water to travel.

This similar concept forces more air into each piston. Air IS fuel for fire just as gasoline IS fuel for fire. In essence you are forcing more "fuel" into the piston via a back draft (aka wave) of pressure when the DISA is closed.


PART 2:

You ALSO give the piston LESS RESISTANCE on the down stroke as you are more rapidly replacing the volume of air due to the added pressure. Think of an air pump. As you pull back on the rod you are forcing air into the pump. If the pump's hose is not connected and open it takes less pressure (aka energy/torque) to pull back on the rod because the volume of air you are drawing (per cubic centimeter) is greater due to the open end (allows more air in). The piston is sucking in air on the down stroke and the wave is helping to fill the cylinder with air thereby causing less energy (aka torque) to be burned for this process. That "extra" energy/torque can now be used to turn your drive shaft a little harder. A directional resonant wave of air is being forced down that piston's throat from the back pressure.



THIS IS ALL THEORY ON MY PART based on the material I have read thus far. It may not be 100% correct but this appears to be the case.

.

Last edited by seemyad; 10-14-2011 at 12:51 PM.
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Old 10-14-2011, 12:40 PM
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Quote:
Originally Posted by champaign777 View Post
it looks like your DISA is not working properly
This may OR may not be the case. All we had prior to your great screen shots was BMW's statement concerning the DISA.

There are a few possibilities:

1) Someone's DISA is not functioning properly (could be yours or ours ).
2) Your car's chip has been programmed to function differently e.g. more power, more torque, or more economy.
3) All of our DISA's work like yours but we don't know it without the tool you have.
4) The screenshot's are not accurately seeing the DISA

Any other possibilities out there?



Quote:
I succeed to activate it on a very short time above 4000 RMP ( cant catch it even but i did it stationary and not on the road )

Cant activate it before 4000 RPM
.
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  #20  
Old 11-25-2011, 11:01 AM
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For the cross linked record, since this is the canonical thread on how the DISA works ... this question was asked today over in the E46 side of the house:
- E46 (1999 - 2006) > DISA valve question

Quote:
Originally Posted by bleedin_nuckles View Post
The DISA valve has a couple of things that look like vacuum pots, but I don't see a hose to go to it. Does it get vacuum from somewhere else, and is the hole in one of the pots just a bleed hole to let air in or out?
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  #21  
Old 04-15-2012, 02:46 PM
Walopower Walopower is offline
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Mine y.2001 525iA DISA work just like yours and also my friend y. 2001 525i works just like this.

Last edited by Walopower; 04-16-2012 at 12:17 AM.
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  #22  
Old 12-27-2012, 05:03 PM
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For the record, here's a pic of a bad DISA valve today:
- > E39 (1997 - 2003) > More trouble codes....

Attached Thumbnails
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #23  
Old 03-10-2013, 01:58 PM
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For the record, this post today was referred to here for the vacuum details:
Quote:
Originally Posted by FiveDriver View Post
Installed a new DISA Valve on my '99 528 (thanks to MAX at Oembimmer). I noticed immediately that the acceleration is much smoother thru the RPM range. Neat little gadget, that DISA.

I have a question for this Learned Assembly -- After the install, I see the Vacuum Guage on the Instrument Cluster is spending a lot more time down on the "0" end of the scale than it used to. Is the vacuum reading corelated to the DISA ??
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #24  
Old 11-15-2013, 11:52 PM
DidusE30 DidusE30 is offline
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Why ma DISA open the flap below 2000 rpm (+/- 1700) ?

I checked two other disa in my car and each opens in the same way.

Last edited by DidusE30; 11-17-2013 at 02:54 AM.
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  #25  
Old 03-19-2014, 12:13 AM
Walopower Walopower is offline
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Quote:
Originally Posted by Walopower View Post
Mine y.2001 525iA DISA work just like yours and also my friend y. 2001 525i works just like this.
And it was broken silicone membrane in vacuum chamber...
Maybe this can replace a vacuum actuator from some other car ignition leveller, or low leak vacuum piston, or even elektric solenoid...
If there is a vacuum leak in membrane, then vacuum is not enough in idle, but can enough in higher rev...
Broken DISA cause Lean codes and even misfires!
It can monitor with INPA, if short term fuel trim. is close to ok when idle, but go fastly worse when press pedal and are ok, or even rich (because long term trim.) over 4000rpm. Then it is surely DISA!
Broken vakuum hoses and leaks in intake manofold or CCV cause that it runs lean in low rpm. allways!
Broken lamda cause difference between banks, poor fuel pressure cause that it runs lean in higher rpm.s I think.
Mine fuel filter was not problem, even it was driven over 150miles in hard winter conditions!

Last edited by Walopower; 03-19-2014 at 12:24 AM.
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