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it is long time I have this issue, it doesn't show any fault codes, or anything, just occasionally pops from somewhere near MAF.
It is louder, when air filter removed.
Please take a listen at the video. Sound comes around 19th second.
What could cause that sound? https://www.youtube.com/watch?v=AMPa...ature=youtu.be
My guess is broken flap inside intake manifold. If you have STAR you can actuate flaps and listen for the noise.
I don't have star, but I have icarsoft. I have to check it, if it shows open/closed position. How should it be called in scan tool? I doubt it will be flaps.
Is there any other method of diagnosing it, or just to remove and look inside?
Try to test components Y22/6 (variable intake manifold switchover valve) and Y22/9 (intake manifold tumble flap switchover valve)
You can also try to test throttle valve (M16/6)
I've been to official mb dealership today, and talked with mechanic, who told me, that it has nothing to do with intake manifold, as it would throw a code, if that would be the case. He told me it is simply misfire, but it takes some diagnostic in which cylinder, and why.
What's Your take on that?
If the intake manifold lever is not broken you will not have a code since the sensor will be able to read flap position.
I would start troubleshooting wit testing intake manifold flaps. With STAR this should be easy 5 minutes test and then you can exclude this as a root of the issue.
Also you can try to disconnect the MAF as suggested by konigstiger. This will be also easy and quick test. When you had the spark plugs replaced last time?
If the intake manifold lever is not broken you will not have a code since the sensor will be able to read flap position.
I would start troubleshooting wit testing intake manifold flaps. With STAR this should be easy 5 minutes test and then you can exclude this as a root of the issue.
Also you can try to disconnect the MAF as suggested by konigstiger. This will be also easy and quick test. When you had the spark plugs replaced last time?
I don't have star, so it is not very easy. I will try to disconnect MAF, and see if that will change anything? With MAF disconnected it should not move that flap, or what?
I have replaced plugs very recently, and I have just cleaned em with wire brush couple of days ago, as I was changing chain.
With MAF disconnected the ECU will use default values for air/fuel mixture.
How long you have to wait for the pop? The engine is hot or cold when the pop occurs? Can you hear it only when IDLE or if you driving as well? When you heard the sound first time? Did you hear it before spark plug replacement?
With MAF disconnected the ECU will use default values for air/fuel mixture.
How long you have to wait for the pop? The engine is hot or cold when the pop occurs? Can you hear it only when IDLE or if you driving as well? When you heard the sound first time? Did you hear it before spark plug replacement?
Hey, I've done some testing now.
So it takes like a minute for that sound to come up, after cold start. During some pops engine shakes a bit, like misfire. When engine reaches operating temperature, pop becomes less frequent. When disconnected MAF it pops much more often, like flaps tumbling all the time. I never heard it while driving, because of wind and engine noise. I'm not sure, but it is possible, that it came after spark plug replacement. Although I don't know how it could be connected to MAF? Also I've found values for B28/10 (right intake manifold tumble flap position sensor): Hall sensor 4.92V; and B28/9 (left intake manifold tumble flap position sensor): Hall sensor 4.95V.
Also I've noticed small oil leak under MAF.
Last edited by Simonas.st; 01-31-2020 at 11:45 AM.
Also I've found, that there's a practice of removing swirl flaps, to prevent it from failing. What's Your take on that? I have done it to my BMW E60 10 years ago, and all was fine.
BTW, I don't understand, what makes that noise? Could You please explain me?
When the pop occurs do you see voltage change on flap position sensor? Like jump to <4V and then back to 4.95V?
Can you check actual values on your diagnostic? There should be a fault counter and you can monitor each cylinder in case there is misfire.
When the pop occurs do you see voltage change on flap position sensor? Like jump to <4V and then back to 4.95V?
Can you check actual values on your diagnostic? There should be a fault counter and you can monitor each cylinder in case there is misfire.
Strangely fault caunter showing 0 an all cylinders, even when it pops and engine shakes a little.
Flap positions are as shown in my screenshot, and not changing much. But I need to check it again on cold engine. These values were pulled at operating temps.
What MAF disconnection has to do with increased popping?
How could I tell if it's a misfire, vacuum leak, or broken flap? Or at least how to rule some of it out of the list?
For broken flap - you can take out throttle body and inspect flaps with borescope. Throttle body is mounted with 4 screws it should be easy to take it out.
You can move swirl flap lever (12/1 or 12/2) with hand left - right, you will see flaps open and close.
Vacuum leak will most likely throw error code and CEL.
For broken flap - you can take out throttle body and inspect flaps with borescope. Throttle body is mounted with 4 screws it should be easy to take it out.
You can move swirl flap lever (12/1 or 12/2) with hand left - right, you will see flaps open and close.
Vacuum leak will most likely throw error code and CEL.
So according to Your explanation, there could be nothing else, just broken flap?
Yes with borescope you will be able to see this. And that's exactly what I think can be wrong, but you need to confirm first. Just to be clear I'm not saying this is the issue, I'm just saying this potentially can be the issue.
Yes with borescope you will be able to see this. And that's exactly what I think can be wrong, but you need to confirm first. Just to be clear I'm not saying this is the issue, I'm just saying this potentially can be the issue.
I might be able to rent one, I have to check it.
I have tried to move flap actuator by hand, while engine running, no sound from there. Also was looking at actuators, when sound pops, they are not moving.
A bit odd. But, maybe if it's broken, and just hanging on the rod, it could cause that sound, independently from actuator movement?
Also, what do You think, why there's no popping, while car is running on "choke", I mean from cold start it takes about a minute, or so for sound to come up.
And thank You for helping me out. I really appreciate it.
Hmm maybe you have backfire through intake. Bad fuel injector can also be an issue. I would check the flaps first to make sure everything looks correct inside intake manifold and start from there.
Hmm maybe you have backfire through intake. Bad fuel injector can also be an issue. I would check the flaps first to make sure everything looks correct inside intake manifold and start from there.
I will. I'm just not sure if go to town to rent boroscope, or just yank manifold out?
It will take few hours to take the manifold out and back in. Also it is recommended to replace gaskets once you take the manifold out. You can purchase cheap borescope camera on amazon.
It will take few hours to take the manifold out and back in. Also it is recommended to replace gaskets once you take the manifold out. You can purchase cheap borescope camera on amazon.
So, I've bought boroscope, but it seems it was too cheap, because it only focus 1inch from it's eye. So I grabbed my phone, and that was much better. Why didn't I thought about it before?
From what I could see, all flaps are moving. What do You think?
01-25-2020, 10:40 AM
