DISA humming continued over a minute after engine turned off

[hillhucker]

As the title says, i've notice twice in the last three days where the DISA (could also be the ICV, but I think the DISA) will continue humming/soft buzzing for a minute or over after the engine is shut off. I know normally it will hum for a few seconds then you can hear the valve shut, but this lasts for at least a minute if not two. I tried turning the ignition on and off, locking and unlocking the doors, but nothing would stop it from humming. It eventually stopped on it's own each time. I did some searches, but nothing pinpointed what i'm experiencing. Any ideas? Thanks

Oh! btw, this car did have the DISA replaced at 71,000 miles on Jul '08. IT has 111,000 right now.

[MrMaico]

They all do that I think. It's neither of those two though but I forget what it is exactly. Secondary air pump maybe? It's something to do with the pollution control system.

[hillhucker]

hmm...i'm not sure. I think it's the disa because when the humming stops i hear a valve shut. It's not the first louder valve shutting, but the second quieter one. Most of the time it only lasts 5-10sec but i've caught it going for over a minute...

[Hornung418]

SAP also has a valve. Which is very prone to failure as water can enter and rust it. So if you are hearing a valve shut it could be many things. I wouldn't rule out the SAP.

Some facts about the Adjuster Unit or DISA Valve: When the car is off, the DISA is open or de-energized. At idle speed, the DISA is closed. Above 4100rpm ECU opens the flap to allow for scavenging across the intake and closes when you dip below 3750rpm.

[hillhucker]

Alright. i better look into that since both of you suggested that. Thanks!

[hillhucker]

However, just looking, the sap is on the passenger side...the sound is definitely coming from right around the disa area or below

[MrMaico]

Alright. i better look into that since both of you suggested that. Thanks!

I searched for a while yesterday trying to find some info on what I was referring to and didn't really find anything so now I'm not so sure. I just can't see any reason though for the DISA or ICV to be doing anything (for that long) after the car is shut down though. I did find a couple posts saying it's the ICV though so maybe you're right.:dunno

My car does it too but I never really tried to figure out where it's coming from. I'll have to check it out next time I hear it.

[danewilson77]

Are you positive, its not the accessory circuit discharging?

Unplug your disa, before you shut your car off, and see if the hum is still there...

Droid + Tapatalk = FTW!

[MrMaico]

Are you positive, its not the accessory circuit discharging?

Unplug your disa, before you shut your car off, and see if the hum is still there...

Droid + Tapatalk = FTW!

It sounds like a hum, like maybe some type of small electric pump running possibly. I'm not even sure if it does it every time. Like I said, never really worried about it so I haven't tried to find where it's coming from. Just thought it was one of those "they all do that" things. I assumed it was maybe something to do with the fuel vapor recovery system, purging vapors from the fuel tank maybe? I thought I had read something along those lines but now a search isn't turning up much info.

I'll try unplugging the DISA next time I hear it.

EDIT: See posts 10 & 11.....

http://www.bimmerfest.com/forums/showthread.php?t=496928

But if hh is hearing it on the left side of the engine his may be something different.

[hillhucker]

I'm hearing it on the driver's side in the disa/icv/tb area. I'm sure it's nothing to be concerned with, but i will unplug things next time it continues to hum for minutes to rule things out.

[MrMaico]

Just got back from a drive, of course it didn't do it. So at least I know now that it doesn't always happen.

[JayDeeZHP]

I'm hearing it on the driver's side in the disa/icv/tb area. I'm sure it's nothing to be concerned with, but i will unplug things next time it continues to hum for minutes to rule things out.

Like I mentioned the other day, it's probably the throttle butterfly servo motor cycling and re-calibrating periodically. My VW does it pretty often, and if I use the laptop to perform a throttle body reset it'll run through a few cycles for about a minute and makes the EXACT same sound that we heard on your car.

If we could visually see the throttle butterfly while the noise is happening we could put this to rest...

[hillhucker]

Like I mentioned the other day, it's probably the throttle butterfly servo motor cycling and re-calibrating periodically. My VW does it pretty often, and if I use the laptop to perform a throttle body reset it'll run through a few cycles for about a minute and makes the EXACT same sound that we heard on your car.

If we could visually see the throttle butterfly while the noise is happening we could put this to rest...



That's right. Very improbable we could ever catch it while we had the intake off though to prove it.

[JayDeeZHP]

I might try to find my mechanic's stethoscope and we'll pinpoint the exact "thing" that's causing the high frequency noise. I know that on some drive-by-wire cars if the engine is off but you turn the key to the position just before engaging the starter motor (ON) it will allow the throttle body to operate via the pedal for a short period of time. We could try that...

OR we could use a voltmeter and read the voltage from the stepper/servo motor that operates the butterfly as we hear the noise... in any case I don't think it's anything big, and we'll see later this week if my car makes the same noise or not.

[Washburn]

i think my car is eating all the time i drive it. It "burps" after i shut it off every time, after 1 min or so. :) I hear that's normal too, although i forgot the explanation/what's causing it.