Knocking at idle (with video): SOLVED

L

LeeMacca

Member
Hi all,

Ive had my Z4 a few weeks now, so after all the initial excitement I have started to notice the car has a a knocking noise at idle. The car idles fine and steady at 800rpm but I a few times i noticed a slight knocking noise when the rpm drops and can also feel it slightly through my feet. I have found a way to recreate the knocking if I put the air con on etc (essentially some more load on the engine) so that when I apply a touch of throttle and release the revs briefly fall to around 700/750 rpm before settling at 800rpm, its when the revs drop to around 700/750 I get the knocking, It doesn't happen when the engine is idling normally. If I press the clutch in it doesn't seem to happen, although saying that its hard to get the engine below 800rpm with the clutch in even with all the accessories on.

Im not sure whether calling the noise a knock is right, it doesn't have a metallic noise, more of a deeper tone. I've got no CEL's or anything and the car drives perfect, clutch and gearbox feel strong.

Anyway here is a video of the noise, I recorded it in the drivers seat and pointed the microphone on my phone underneath the car. Is it something I should worry about or just keep an eye on?

Lee

[youtube]JzQA8Vu8D0Y[/youtube]
 
I'll give that a check tomorrow. I guess it will be easy to check the DISA valve bearing in mind I can put my ear right on it!
 
So after doing some proper investigation I have found the culprit. Basically one of the heat shields, the one virtually right under the drivers feet has been destroyed and was rattling. I went over a speed bump last week that made a horrible scraping noise, but after the initial rage i forgot all about it and it seems it did more damage than first thought. I'll let the pics do the talking but safe to say the council will get a strongly worded letter, you'll know what I mean when you see the photo of the speed bump that did the damage!

Do I need to replace this part of the heat shield urgently? It doesn't seem tremendously important.

shield_zpsbec6447f.jpg

The speed bump in question!! A complete joke!

humo_zps76c6ec03.jpg
 
You gotta be kidding! How on earth can any council get away with that! Clearly a very badly maintained "speed hump". A council wouldn't have a leg to stand on against any claim you might put in. Do it and don't take no for an answer.
 
You must log in or register to reply here.
Back
Top Bottom