Struggling to locate cause of excess noise

[Tayloi2]

Good afternoon people,

I'm hoping someone may be able to assist me with a couple of issues I am having with my Z4 E85 2.0.

Firstly, I have recently had both solenoids replaced in order to cure a rough idle problem. Subsequent to this the car was then diagnosed with a slack timing chain so I had this replaced too. It's been an expensive couple of months! Car ran like a dream again for about two weeks but EML has come back on with P0420 code - Catalytic Converter Below Threshold. Do we think this is specifically the cat or possibly the lambda sensors? I've checked other topics on here and some are recommending a fuel additive like Wynn's to blast the system. I'm just looking for advice from anyone that has had this issue and the quickest way to resolve. I've got access to a decent indy but he's not cheap so I'm hoping there may be a DIY fix.

Second issue is a weird one. When travelling a speed i.e. 30mph+ there is a metallic whirring sound but I cannot pinpoint where this is actually coming from. Again from other discussions on here, the symptoms don't match up with wheel bearing issue as I suspect it may be.

Any pointers and suggestions on either issue or both are very welcome! Thanks for reading.

 

[road warrior]

if its not a regular beat of metal sound it might be the disk shields have come adrift or bent, they might be rubbing against the disk - jsut a thought, jack up each wheel first and spin the wheel and try that

 

[dhobbs]

To try and eliminate the source you need to vary certain aspects.
Does the sound change with speed, engine revs, steering inputs, clutch in/out, temperature, road conditions etc.

That could point to a particular area such as engine, exhaust, suspension or bodywork.

A common issue is the 2 bulkhead braces in the engine bay, the bolts can be lose.

Good luck.

 

[ph001]

The eml light problem seems to be a fairly regular occurrence on the 2.0l and most people never get to the bottom of it. The cats are built into the exhaust manifold and do have a habit of cracking unfortunately.

 

[AveZ4coop]

Whirring noise could be diff related? What mileage has your car done?

 

[tug]

The emissions light is very common on the 2.0i. I used to get it come on randomly and often. Any cheap OBD2 reader will clear the light but to stop it coming back on you need to give it some beans regularly. I drive mine enthusiastically when possible taking the revs up to 4000 through the gears and never have the light come on at all now.
But havin said that, if i get stuck behind a doddering old git when it is raining or damp weather then the light will come on occasionally. I have come to accept it and just plug in and turn it off.

So just open the zed up when possible and it will keep the light away. In my experience of owning my zed for 5 years the N46 loves to be thrashed.

Cheers, tug

 

[Ewazix]

If You search for info on cracked exhaust manifold on the 2.0 you will find it's a common headache that causes random emissions codes and can apparently be hard to trace.

 

[tug]

Yes mate, mine was cracked and had to have it TIG welded. Good as new now but getting stuck occasionally behind some old dear who has spent her pension on a new Q7 and has no idea what to do with it! :lol: i still very occasionally (especially if it is raining or damp weather :idunno get the light up again :thumbsdown: but i just turn it out. Its always the same code P4050 or something like that, 'below threshold' but never failed the MOT so im good with that.

Cheers, tug