I'm confused how to properly test for DISA valve proper operation on the BMW E39

I'm confused how to properly test the DISA valve on the E39.

Today, after seeing ForcedFirebird's pictures of the inside of a bent exhaust and pitted intake valves in the #3 cylinder due to the DISA (DIfferenzierte SAuganlage - "Differential Air Intake") flap failing ... and then moments later, reading of Ågent99's smog-test saga where the DISA valve seemed to have been the culprit ... and then seeing cambrian123456 post where in the process of cleaning the ICV, he notices his DISA valve is filthy ...

And, earlier this week, DominguesE30 asked the similar question of how to test the DISA valve (without much response).

I got to wondering how to "really" TEST the DISA valve in the BMW E39.

Doing the obligatory searching ... I find a confusing jumble of tests:
- These pictures show varnish buildup (presumably that's a visual test)
- This picture shows the flap missing (another visual test)
- Poolman gave a noise/performance DISA test here
- ventsyv added a DISA rattle test here (another noise test)
- Ågent99 alluded to a "smoke test" here (a visual test for vacuum leaks)
- szee1 alludes to the "resistance" of the DISA flap here
- dakarm also alludes to the "resistance" of the DISA flap here
- Lbert says to check the condition of the o-ring DISA gasket here
- uncmozo mentions specific codes thrown here that implicated the DISA valve
- This rebuild DISA article says codes will be your first sign of malfunctioning
- This related DISA article says you'll get a misfire if the o-ring leaks

But I see no real diagnostic tree for the DISA valve.

Maybe it's time to start one?

Bluebee- I too was plagued by this scenario... I had been battling a pretty bad idle stumble, and I inspected my DISA to the best I understood and had ruled it out-and moved on. When I finally gave up and brought the car in to the mechanic (I thought it was a vacuum leak that I couldn't find) it turned out to be the DISA. The mechanic "bench tested" it somehow. The car is back in the shop today for some unrelated stuff but when I pick it up I'll try to ask him how exactly he tested it.

It will usually pull intermittent P0171 and P0174 codes (running too lean on bank 1 and 2) - like a vacuum leak. Keyword is intermittent - like once a week. If the interval starts getting shorter you're in trouble.. Also, the DISA starts making noise.
Pulling out the DISA, if the valve is sloppy (no resistance) - she's on the way out.
If you just pull it out to check it, you better have some replacement O-ring which you can source from e-bay seller jdm-auto. Linky.
That is if the DISA is still OK. No sense shelling out 200 bux (yet).


P.S.: for clarification: the first thing to go is the resistance of the flapper. More air gets sucked in - like unmetered air (that's why the codes start popping up). This combined with the noise (you have to open the hood and hear close to the intake manifold. A helper should rev the engine) is a dead giveaway. Doing a vacuum leak test (smoke test) will reveal nothing - pretty much pinpoint the culprit. Also some stumbling when you step on it.
This is all the info I could gather over different forums.

The way I was taught to test the part--with the engine running lean over and put your left ear on the part--if you hear it rattling and making racket--it's bad--if it's silent it's OK--Rajaie was the one who informed me of the test--

An ingenious proposal for testing the DISA valve is in this thread today:
- DISA Activation Fail

The mechanic proposed placing a white dot in the location shown below; then at the proper RPM, the dot should 'move' one way, and then at the next RPM cut point, it should move the other way (the theory goes).

According to RDL, (m54x5[1].pdf), those RPM points are:

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

Reference: Pages 42 -44 of the attached document.

For the record, this E46 thread today referred to the following DISA valve test video for the M54 engine (same engine as many E39s):
- E46 (1999 - 2006) > Bad DISA w/o codes?

.

For the crosslinked record, today, this thread shows an important point:
- Bingo!! I may have solved the misfire and lean codes P0171, P0174, P0300

Not only is the DISA responsible for some misfires, but, it can ruin your engine if you don't check it every 100K miles or so.




- 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).

Originally Posted by bluebee

For the crosslinked record, today, this thread shows an important point:

Originally Posted by bluebee

- Bingo!! I may have solved the misfire and lean codes P0171, P0174, P0300

Not only is the DISA responsible for some misfires, but, it can ruin your engine if you don't check it every 100K miles or so.

I said it will pull those codes - Post #3. And I also raised awarness a while ago that at around 90 k miles the DISA is on the way out.....

Originally Posted by doru

I said it will pull those codes - Post #3. And I also raised awarness a while ago that at around 90 k miles the DISA is on the way out.....

I had forgotten who had warned us, and I thank you for doing so!

It would be nice if we work on a group buy for a decent deal, both ways, with one of the sponsors. I'm not sure how to go about setting that up.

As for testing the DISA, here's another reputed test, in vitro:
- Bingo!! I may have solved the misfire and lean codes P0171, P0174, P0300

Originally Posted by teklord69

I saw a video somewhere on how to test the vaccum on the valve. Move the flapper to the closed position, then block the vacuum hole with your finger. Release the flapper and it should not open all the way. It will stop in the middle position and wont open fully until you let go of your finger.

There is another suggested DISA unit test procedure from this thread below:
- E39 (1997 - 2003) > Car was throwing codes....DISA valve!

Originally Posted by uncmozo

If you didn't want to remove the valve, there is a small odd-shaped cover that easily snaps off with a small screwdriver. It's on the bottom right of the rectangle that is the main body of the valve. If you pop the cover off, you can manually actuate the valve. I would guess you could actuate the valve with engine running, and diagnose if the flap is working or not. I found this out after trying to take the old valve apart.

Since I have the following codes, I decided today to remove my DISA for a look:

1. P1083,BMW 202, Fuel Control Limit Mixture Too Lean (Bank 1 Sensor 1)
2. P1085,BMW 203, Fuel Control Limit Mixture Too Lean (Bank 2 Sensor 1)
3. P0174,BMW 228, System Too Lean (Bank 2)
4. P0171,BMW 227, System Too Lean (Bank 1)

To remove the DISA was easy.

• I removed the electrical connector to the DISA
• With a hinged socket set, I removed the lower T40 Torx bolt
• I removed the upper T40 Torx bolt
• I removed the DISA (pressing down on one vacuum wire to provide room)
• NOTE: I did not remove ANYTHING else (no MAF, no hoses, no battery connection, no nothing)

The one thing I should have done beforehand is that I should have purchased an aftermarket M54 DISA o-ring:
- Where to get just the DISA valve o-ring (1)




I wanted to innervate the DISA electrical connection to see if it would operate at either 5 volts or 12 volts; but I figured I'd check here first.

Q: Does anyone know if a 6 volt/12 volt battery charger can be used to test the DISA valve electrical operation?

Originally Posted by bluebee

Q: Does anyone know if a 6 volt/12 volt battery charger can be used to test the DISA valve electrical operation?

It looks like the test is to use 12 volts (based on this thread):
- E39 (1997 - 2003) > DISA Activation Fail

- The 12 volt test

Originally Posted by VitaminXX

The mechanic applied an external 12V power source to activate the valve, the white mark did not move also. He told me my DISA is bad.

From that same thread, it looks like these are additional DISA diagnostic test procedures:

- The moving dot test

Originally Posted by VitaminXX

The mechanic ... marked a white point on the DISA valve... He told me normally when I start the engine up and step on the gas to let the RPM up to around 3000, the white mark should move to right accordingly since the DISA is regulating the air flow. However, as I stepped on the gas, the white point did not move to right.

- The unplug test

Originally Posted by VitaminXX

The mechanic unplug the DISA terminal, nothing happened.

- The GT1 test

Originally Posted by VitaminXX

When I got home, I used my GT1 to activate the DISA valve, it seems the white mark did not move either.

And, from post #10 of this thread, comes these two videos for testing purposes:
- X3 E83 (2004 - 2010) > CCV time, oh and DISA too.

- The rattling noise test

Originally Posted by poolman

the way to make the test is, with the engine at idle lay your left ear over on the disa. If you hear rattling and such inside the box,it's bad and needs replacing.

Originally Posted by szee1

It appears that unplugging the DISA connection should stop the noise.That said, I am not sure that unplugging it always eliminates the noise. I have read that you can also place your ear on the DISA while the engine is running and verify if noise is coming from it. From what I can gather, the failure points can either be a loose valve on the shaft or a failure in the vacuum system which creates the noise. Mine was a loose shaft and I don't recall any noise from it.

This is a good link to show how the valve is connected to the vacuum actuator.


DISA noise video.

The autopsy test:
- E39 (1997 - 2003) > DISA Autopsy

The ribbed-o-ring test:
- E39 (1997 - 2003) > DISA 0 Ring

You can't test something until you know how it works normally.

To that end, this explanation helps with any voltage tests we may run:
- E39 (1997 - 2003) > DISA Autopsy

Originally Posted by AnotherGeezer

After much research I found this to be the best DISA operation description 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."