[Phil325i]

Could any of you NA (N53) guys pop your hood and see of your engine makes the same noise as mine? When I blip the throttle, just before the falling revs drop down to idle, there's a 'clunk' noise from the intake/throttle area. It's like the noise on this clip at 0.15 seconds:

General opinion on YouTube is that it's normal, but I'd like confirmation...while I still have a warranty!

[Three_thirty_I]

This engine still uses the throttle body for throttle unlike the N52 which simply opens and then uses the Valvetronic, so wondering if this is not what you are hearing since it is happening when opening and closing the throttle. Also the DISA flaps could be part of this problem, but I think mainly the throttle body is worth looking at. With this being direct injection (and have heard that they tend to be noisy) not sure how this plays into the noises being heard. Sounds like a bag of marbles rattling around in the intake!

Is this heard while driving too?

[Phil325i]

Originally Posted by Three_thirty_I

This engine still uses the throttle body for throttle unlike the N52 which simply opens and then uses the Valvetronic, so wondering if this is not what you are hearing since it is happening when opening and closing the throttle. Also the DISA flaps could be part of this problem, but I think mainly the throttle body is worth looking at. With this being direct injection (and have heard that they tend to be noisy) not sure how this plays into the noises being heard. Sounds like a bag of marbles rattling around in the intake!

Is this heard while driving too?

Thanks. No, not heard while driving. And it can't be DISA flaps... because the 325i 3-litre doesn't have them - only the 330i.

[Three_thirty_I]

Originally Posted by Phil325i

Thanks. No, not heard while driving. And it can't be DISA flaps... because the 325i 3-litre doesn't have them - only the 330i.

The 330i has 2 DISA flaps, but the 325i should have 1 like the N52B25 - open to correction, but should be right.

The 325i should have the 2 stage intake which requires 1 DISA flap...

[Phil325i]

Originally Posted by Three_thirty_I

The 325i should have the 2 stage intake which requires 1 DISA flap...

Thanks. Learn something new every day! Even more to the point:

1) Do DISA flaps make that clunk noise when they close and...
2) Does your 330i make the same noise?

[Three_thirty_I]

Originally Posted by Phil325i

Thanks. Learn something new every day! Even more to the point:

1) Do DISA flaps make that clunk noise when they close and...
2) Does your 330i make the same noise?

They can generally make a rattling noise. Well mostly the older types like the M54 engines in the E46, but even the N52/3 motorised DISA flap does make a noise when it actuates, but not to this extent if working normally. I replaced mine thinking that they were making the pinging noise (as in therefore not pinging), but they weren't. When I experimented with my diagnostics cable and INPA I was able to actuate each DISA flap and they made a noticeable clunk noise. But this is with the engine off so pretty quiet in reality and never heard when revving the engine.

I would have the codes read to see if anything comes up. Also, maybe worth pulling the throttle body out to see if there is anything obviously wrong, loose butterfly valve etc. The DISA flap is less likely to be the issue I reckon though.

Now with my problem and searching the internet for similar symptoms, I am sure that I came across one of two vids of N53 engined E90's that had a very similar noise to what yours is doing. So might be worth searching YouTube to see if there are any other vids of this - maybe they have indicated what caused their problems...

[Johnny D]

No DISA valves on the motor in the video. You can see both of the connections above the throttle body clipped onto the intake manifold. This is a new one to me. I would take it in and get it checked.

[Three_thirty_I]

Originally Posted by Johnny D

No DISA valves on the motor in the video. You can see both of the connections above the throttle body clipped onto the intake manifold. This is a new one to me. I would take it in and get it checked.

Hmm, I thought it was only the 323i variants that had no DISA flaps???

[Phil325i]

Had the car inspected today by my friendly indy. He is sure the noise is coming from the throttle body (the butterfly actuation mechanism). He checked with a contact in BMW and very few of these bodies are replaced, so I'm coming to the view (in the absence of any other symptoms) this noise is probably normal.

But if anyone else out there with an N53 could check the noise thiers makes (or doesn't) I'd be grateful...

[Three_thirty_I]

Originally Posted by Phil325i

Had the car inspected today by my friendly indy. He is sure the noise is coming from the throttle body (the butterfly actuation mechanism). He checked with a contact in BMW and very few of these bodies are replaced, so I'm coming to the view (in the absence of any other symptoms) this noise is probably normal.

But if anyone else out there with an N53 could check the noise thiers makes (or doesn't) I'd be grateful...

Did he remove and inspect it? Hopefully onto something here!

[Phil325i]

Originally Posted by Three_thirty_I

Did he remove and inspect it? Hopefully onto something here!

No removal or dismantling I'm afraid. Just closely listened for the source of the noise while I blipped the throttle. I may take off the inlet hose to see if anything's obviously amiss...

[Phil325i]

I've found two more clips with the identical noise. This one (between 0.0 and 0.10):

http://www.youtube.com/watch?feature...&v=Yi-fxH_HTNo

and this one (at 0.25):

http://www.youtube.com/watch?feature...&v=1xLml8MAe1M

So I'm even more convinced now it's a normal function of the operation of the throttle. More feedback welcome...

[Three_thirty_I]

Originally Posted by Phil325i

I've found two more clips with the identical noise. This one (between 0.0 and 0.10):

http://www.youtube.com/watch?feature...&v=Yi-fxH_HTNo

and this one (at 0.25):

http://www.youtube.com/watch?feature...&v=1xLml8MAe1M

So I'm even more convinced now it's a normal function of the operation of the throttle. More feedback welcome...

I am sure one of these it the one that I saw that I mentioned above.

Now the previous N52 also has a throttle body, but from my understanding it simply opens all the way and lets the Valvetronic control the throttle, so it's actually just there as a redundancy in case the Valvetronic fails.

Just for interest sake, this is what my N52B30 sounds like, bear in mind that I took this video to check to see if there was any abnormal movement of the tensioner pulley which there wasn't of course. So the vid has some revving and normal blipping of the throttle (open and closed), but again, throttle body would remain open with the Valvetronic actuator controlling the throttle.

http://www.youtube.com/watch?v=WQ3niNqX-CI

I would take the air box out, then remove the intake boots and then the throttle body, just a few basic tools if it is anything like the setup on the N52 - same Euro air box for a start...

Should look much like this.




Air box out with the intake boot still on, and then off and the throttle body out.

[Phil325i]

OK update on the throttle 'clunk' issue. Turns out it is a problem. Fault code reveals an issue with the throttle stepper motor. The oxygen sensor post-cat is also down, though whether one caused the other or not, I don't know.

More info when new throttle and sensor fitted...

[Three_thirty_I]

Originally Posted by Phil325i

OK update on the throttle 'clunk' issue. Turns out it is a problem. Fault code reveals an issue with the throttle stepper motor. The oxygen sensor post-cat is also down, though whether one caused the other or not, I don't know.

More info when new throttle and sensor fitted...

Wow, okay well that's at least good news that you know what you are dealing with (wish mine was as easy as that)! Hopefully they will have your car in good health soon!!!

Keep us updated!

[Phil325i]

Interim update. Had new throttle body fitted. Noise disappeared and car ran much smoother...for a day! Noise has now returned. Arghhh! Back to my indy to have any fault codes read...but I get the feeling this one could run and run.

[Three_thirty_I]

Originally Posted by Phil325i

Interim update. Had new throttle body fitted. Noise disappeared and car ran much smoother...for a day! Noise has now returned. Arghhh! Back to my indy to have any fault codes read...but I get the feeling this one could run and run.

That's weird! And annoying!

[Phil325i]

Originally Posted by Three_thirty_I

That's weird! And annoying!

You're not kidding. The mystery deepens...absolutely no fault codes. Beginning to wonder if it is normal after all. My indy is making inquiries with BMW Tech...