Exhaust butterfly valve stuck open

[int2str]

Hey guys!

It seems like I have an unintentional "Golf Tee mod". The exhaust valve on my 330i is open all the time. At least when the car is off or when the car is idling. Can't test much beyond that of course.

The valve should be closed at idle, right?
Any idea what may have caused this?

I know some of you keep it open intentionally, but I drive my car a lot harder than most probably and can definitely notice a distinct lack of torque around 3-4k RPM. I'm suspicious that the valve might be causing this.

Thanks!

[Critter7r]

The valve's sole purpose in life is to keep the car quieter at modest driver input. It open up when the gas pedal request is over 40-60% and/or over 3000-4500 rpm (both conditions vary based on the gear the transmission is in at the time). The valve being stuck open will not cause a lack of power.

[MBVan]

Mine is also stuck open. I found out that the solenoid that turns vacuum on and off is receiving 12 volts at the wiring that connects to it, yet the solenoid does not react ( meaning that it makes no difference if it is getting power or not; it always stays shut and does not allow vacuum to reach the butterfly valve and close it.) A faulty solenoid perhaps? Maybe, but why then does it start working when I apply power straight from a jump starting battery. Perhaps the power coming through the cars wiring is going through a fuse that is not letting enough amps through to open the solenoid? I'll have to try swapping in different size fuses, but I'd like to know if a fuse that is rated wrong could be at fault, or is it just a bad solenoid?

[mryakan]

What do you mean by a fuse rated wrong does not pass enough current . A fuse rating has to do with the maximum current it can pass through before melting and cause an open circuit essentially stopping the current flow. Putting a different rated fuse does not impact the current flow through the circuit since it has minimal resistance and is basically a shunt closing the cicuit until it blows due to excessive current draw from the component and thus protecting the component.
Do not put higher rated fuses or you could fry a component or worse, start a fire.

[MBVan]

What do you mean by a fuse rated wrong does not pass enough current . A fuse rating has to do with the maximum current it can pass through before melting and cause an open circuit essentially stopping the current flow. Putting a different rated fuse does not impact the current flow through the circuit since it has minimal resistance and is basically a shunt closing the cicuit until it blows due to excessive current draw from the component and thus protecting the component.
Do not put higher rated fuses or you could fry a component or worse, start a fire.

Thanks for clearing that up. Then the solenoid must be the culprit.

int2str, I believe you have the same problem. Check to see if you're getting power at the solenoid connection. If you are, then the solenoid should be open and let vacuum reach the butterfly valve, thus closing it. In your case, your solenoid is either not opening (broken solenoid) or then you have a vacuum leak either before or after the solenoid. To test for vacuum, you can use your finger to see if the vacuum hose is "sucking." It is pretty powerful ( about 20 inches of mercury) so you will feel the vacuum if it is present.
Also, if you're not getting power from the wiring with your ignition on, then obviously you have an electrical problem. Also check to see if your butterfly valve moves freely.

[int2str]

The valve's sole purpose in life is to keep the car quieter at modest driver input. It open up when the gas pedal request is over 40-60% and/or over 3000-4500 rpm (both conditions vary based on the gear the transmission is in at the time). The valve being stuck open will not cause a lack of power.

I don't agree with this. But it doesn't matter really. If the valve is supposed to be closed at low RPM, I'd like it to be closed. No matter what it does or doesn't do.

Thanks for clearing that up. Then the solenoid must be the culprit.

What is this solenoid you speak of? Where is it located?
I was under the impression the valve is simply operated by the vacuum pressure that the engine generates. Why would a solenoid be required?

Check to see if you're getting power at the solenoid connection. If you are, then the solenoid should be open and let vacuum reach the butterfly valve, thus closing it. In your case, your solenoid is either not opening (broken solenoid) or then you have a vacuum leak either before or after the solenoid.

Where is the solenoid?

To test for vacuum, you can use your finger to see if the vacuum hose is "sucking." It is pretty powerful ( about 20 inches of mercury) so you will feel the vacuum if it is present.

Is there an easy way to do this?
Not sure I want to mess with the vacuum hose near the valve since the exhaust will be hot....

Also check to see if your butterfly valve moves freely.

It does move freely. Well, it does require some force to move, but I think that's simply the spring load.

[MBVan]

The solenoid is located in the trunk of the car below the left tail light behind the trunk liner/ matting. You'll need to remove the carpet liner covering the left side of the trunk space to access the solenoid. The solenoid is an electrical valve that is open when at idle and low revs. The power to the solenoid is cut off at higher revs, thus closing the solenoid valve and subsequently cutting off vacuum to the butterfly valve. The solenoid is needed because the vacuum at high revs is still powerful enough to keep the butterfly valve closed.
You don't have to check for vacuum at the muffler. You check it at the solenoid in the trunk while your car is running.
Remove the two hoses connecting to the solenoid. Check to see if you're getting vacuum to the solenoid from the vacuum hose that comes from the front of the car. If you are getting vacuum, then connect the vacuum hose back to the solenoid. Next, check to see if the solenoid is open and letting the vacuum pass through. You do this by placing your thumb on the solenoid barb to which the last vacuum hose connects to (the one that goes to the butterfly valve.) If you're getting vacuum there, then the hose that goes from the solenoid to the butterfly valve is leaking and needs to be replaced. If vacuum is not passing through the solenoid while the car is running, then you need to check if you're getting power from the wiring that connects to the solenoid (if you're getting power and the solenoid is not opening and letting vacuum through, then the solenoid is broken) If you're not getting vacuum from the vacuum hose that comes from the front of the car, then you have a leak between the intake manifold and the solenoid.

[int2str]

Great info, MBVan!
Won't be able to check tonight, but I will definitely try your diagnostic tips tomorrow.

Just a quick update:
Stuck my head in the trunk briefly to check things out. I found the solenoid through the tail light access panel - it's tiny! I can't get the hoses off easily from there, so I'll have to take some more time tomorrow to get the whole liner removed there.

[MBVan]

I'm in the process of ordering the solenoid from partsgeek.com Price is $36.75 It's called an Electric Change Over Valve on partsgeek.com in case you want to order the part from there. The SKU number is W0133-1624906.

I will let everyone know if it fixes the problem.

Currently I have the two vacuum lines connected straight to each other, and the butterfly valve stays closed. The solenoid is the only thing that can be damaged because it gets power from the wiring, yet it does not let vacuum through.

[int2str]

Alright, I ripped out the trunk liner and got access to everything nicely. If I hold the hoses up against each other, the valve closes. So the valve is working and the vacuum is sufficient.

I took the solenoid out and bench tested it. If I apply 12V to it, it does indeed open up. But if I just idle the car, it doesn't open.

So first a general question just so I understand:
When the car is idle the butterfly valve should be closed? Correct?

My multimeter is currently broken, so I can't test the connection to the car right now. But lets say I get the meter going again and I notice that there is no current on the solenoid plug. What would cause this and how do I fix it?

Broken wire? Computer malfunction? Fuse burnt out?

Thanks!

[MBVan]

Alright, I ripped out the trunk liner and got access to everything nicely. If I hold the hoses up against each other, the valve closes. So the valve is working and the vacuum is sufficient.

I took the solenoid out and bench tested it. If I apply 12V to it, it does indeed open up. But if I just idle the car, it doesn't open.

So first a general question just so I understand:
When the car is idle the butterfly valve should be closed? Correct?

My multimeter is currently broken, so I can't test the connection to the car right now. But lets say I get the meter going again and I notice that there is no current on the solenoid plug. What would cause this and how do I fix it?

Broken wire? Computer malfunction? Fuse burnt out?

Thanks!

int2str, That's the same problem I'm having ( as I wrote earlier in this thread) I also bench tested the solenoid and it worked, but not in the car even though I did receive current at the plug/wiring that connects to the solenoid. So, I can only believe that the power from my booster battery was enough to make the defective solenoid open, but the power coming from the car's wiring is not powerful enough to make the defective solenoid open.
Perhaps the solenoid could be cleaned and loosened so it would start opening and closing again, but I just ordered a new one.
int2str, I don't believe you have an electrical problem. It is probably the solenoid. If you do have an electrical problem, then check all your fuses first, then locate the ground connection that the solenoid wiring uses and make sure it is free of corrosion and also that it is securely tight. If that does not fix it, you need to trace the positive wire that connects to the solenoid and make sure that it is not shorting to ground anywhere because of damaged/stripped insulation etc..
It is unlikely though that you have electrical problems. Next step is to test for voltage at the plug. If you're getting voltage, then assume the solenoid is kaput.
Yes, I believe that the butterfly valve should be closed at idle. I've read so in many posts so I believe it is so.

[fshubert]

Oh heck, leave the butterfly open. It sound nicer.....

[02325]

wether the valve is open or closed it really doesn't effect anything. most of those damn thing vibrate/rattle and we have to fix them. the correct way is to replace the muffler, but we just make them stay open so they dont rattle.

They only make the car quiter at idle, but who really cares, if you dont like the noise move somewhere else.

[MBVan]

I replaced the electrical solenoid (valve) but it did not work, meaning the solenoid did not open as it should. I'm getting 13.6 volts at the electrical wiring connector, but for some reason the valve does not react even though it is getting voltage. If I bench test the solenoid with a jump start battery, then it works and makes a clear "click" sound. ????????????? Are there any electrical experts who can explain this weird situation?

[Critter7r]

Can't say for certain on the E90... but on my E46, the butterfly in the muffler is held open with a spring until the solenoid closes it. However, E46 butterflys are vacuum actuated, so the setup may be different with the electric solenoid on the E90s. I guess all I'm saying is that when voltage is applied to the solenoid, maybe that's what holds the butterfly closed, and releasing the voltage allows the butterfly to open.

[MBVan]

Can't say for certain on the E90... but on my E46, the butterfly in the muffler is held open with a spring until the solenoid closes it. However, E46 butterflys are vacuum actuated, so the setup may be different with the electric solenoid on the E90s. I guess all I'm saying is that when voltage is applied to the solenoid, maybe that's what holds the butterfly closed, and releasing the voltage allows the butterfly to open.

My car is an E46. Yes, you are right. When voltage is applied to the solenoid, it clicks open and lets vacuum pass through to the butterfly valve thus closing it. My problem is that the solenoid (old and new one) do not open eventhough I am getting voltage in the car, but if I bench test the solenoids, then they click open like they should.

[Critter7r]

Usually, BMW electronics work exactly the opposite of what you'd expect. Take this solenoid... the car is probably ALWAYS suppying voltage to the solenoid, and when it wants to activate the solenoid to close the butterfly, it'll send a GROUND signal to complete the circuit and activate the solenoid.

So make sure you're getting a ground signal at the solenoid, too.

[MBVan]

Usually, BMW electronics work exactly the opposite of what you'd expect. Take this solenoid... the car is probably ALWAYS suppying voltage to the solenoid, and when it wants to activate the solenoid to close the butterfly, it'll send a GROUND signal to complete the circuit and activate the solenoid.

So make sure you're getting a ground signal at the solenoid, too.

Interesting. By "ground signal" you mean that the ground wire is grounded = continuity on a voltage meter set to measure resistance (ohms).
Thing is, the way I tested for voltage was by placing the positive lead of the multimeter to one prong of the electrical connector, and the negative lead to the other remaining prong on the electrical connector. Then I measured over 13 volts, which means that the circuit is complete, to my knowledge.

[Critter7r]

Hmmmm... I would think so too. But then again, I know just enough about this particular subject to be dangerous.

Is it possible that your butterfly is just stuck? That might make it seem like the solenoid isn't reacting to the voltage signal (or ground signal), when really, it's trying to, but just can't overcome the sticking butterfly?

[MBVan]

The butterfly moves freely. Right now I have bypassed the solenoid so vacuum goes straight to the butterfly valve at all times. A stuck butterfly valve is not the issue. This is a really weird problem. I'm wondering if the ECM would cut off power for some reason when I connect the solenoid to the wiring? Or is my car playing tricks with me

[int2str]

MBVan, any update on this?

[MBVan]

int2str, nothing new yet. I have not worked on the car for a while, but I will continue with the work by next week. I suspect something very simple is the cause of all the trouble. I will post back later with an update.
Meanwhile, int2str, did you get a voltage reading at the solenoid wiring?
If you do get voltage, then we are both in the same boat (we get voltage and the solenoid works when bench tested, but does not work in the car).

[redlands]

i asked the service forman at my dealer about my 335, and he says that the valve has absolutely nothing to do with performance, it is purely for sound. anyway haw could something that restricts your exhaust help performance? the whole point behind performance exhausts is to be less-restrictive??? its your imagination

[Critter7r]

i asked the service forman at my dealer about my 335, and he says that the valve has absolutely nothing to do with performance, it is purely for sound. anyway haw could something that restricts your exhaust help performance? the whole point behind performance exhausts is to be less-restrictive??? its your imagination

he's right, though, it is just for sound. The two pipes you see on the outside of the muffler... well, once they get inside the muffler, the become one pipe (or... they originate as one pipe inside the muffler and then - inside the muffler - they split into 2 pipes). So no additional exhaust comes out when the flap is open, it just changes the resonance of the sound coming out.

Imagine pouring water through a funnel (the funnel is your muffler)..... now imagine putting a split Y-pipe on the end of that funnel (the y-pipe is your 2 pipes that come out of your muffler). No additional water is going to flow through that funnel, but it'll sound different when the water hits the pavement.

[MBVan]

I have not worked on the solenoid this week, but it just crossed my mind that the problem may be caused by one of the computers on the car, or whatever module controls the solenoid. It makes sense since the door locks and windows often become funky because of the General Module failing, so possibly the same is happening to the solenoid.