Unusual engine sound

[MayaH]

Hi all!
I just purchased a 2006 Z4, 3.0 si with only 27000 miles.. The car was transported from Pennsylvania to Oregon through harsh winter conditions, and when I first started it, the engine sounded as a diesel engine, A week later, the sound is gone but now when I first start the car, the RPM go up and down several times before they reach an optimal level.
The engine oil was changed by the Dealer (not BMW) few months ago, but I can’t be sure if they used the appropriate type.
Any suggestions?
Thanks!

 

[Street]

Hey welcome to the fold. Seems you've been lurking for the right zed for a while and it sounds like you found a beauty!

Unfortunatley it's near impossible to say what the engine noise is without hearing it. However the n52 engine in the 3.0si is notorious for its 'ticking' sound. It's caused by poor lubrication to the hydraulic lifters over time. If you search youtube you'll find examples and how 3k revs for a few minutes quietens it down as the oil circulates. If that is the issue you can get Hydraulic Valve Lifter treatments to help, but I've not heard of it being detrimental to the engine if left.

How bad is the RPM hunting? Could be a sticky idle control valve or failing MAF sensor. @enuffzed tackled one with pentometer issues.
Equally it could equally just be normal adjustment of the air/fuel mix as she adapts to the different variables.

 

[smorris_12]

When I first got my N52 in April it ticked nastily on several occasions. After a few thrashes round the place using all the revs it's not done it since.

 

[Z4Mariner]

Welcome to 2006 3.0Si ownership ! And only 27K miles !! Though mine is a coupe and has 89K now, I can relate to your experience - I suggest an oil & filter change at your soonest convenience, if only for peace of mind. When you replace the large and small O-rings on the oil filter housing cap, see whether the old ones are brittle or not.

1) Valve lifter clatter: I don't notice this much on my Z4, but I sure did on a 128i I owned. It seemed to be most noticeable on startup from cold after sitting a while (like transit), or under prolonged idle (low rpm w warm oil). It seems to be a BMW N52 trait, but also seems not to be especially harmful. After reading all I could on the subject when I owned the 128i, I agree with the opinion that BMW simply designed the lifters for average higher rpm use (higher oil pressure and flow). Complaints were far higher in the US than in the rest of the world, perhaps because of larger number of customers who loafed their engines. I seldom run my Z4 under 2K rpm except when starting off, and I hardly notice any valve clatter. The oil used matters as well - so if you change the oil and the filter you'll have that base covered.

2) Hunting idle: Your most likely cause is a vacuum leak - I have not had this problem with the two N52 vehicles I've owned, but I sure did with the M54 in my former 325xi. I thought that a leak big enough to cause unstable idle should set engine codes, but it never worked that way for me. I only achieved success by methodically renewing vacuum hoses, O-rings, seals, gaskets, and CCV (PCV) components.

Good luck with your new ride ! Share progress as you get it sorted.

 

[Mr Tidy]

Hi and welcome to the forum MayaH.

It looks like you've had some useful advice already. All I can add is that I've currently got my 4th car with the N52 engine and to some extent they have all suffered from time to time with the ticking from the valve lifters when cold, especially when they haven't been used for a while.

Driving a decent distance to get them properly warmed up then using all the rev range always makes it go away!

Nobody has mentioned photos yet, but we would love to see some of your car.

 

[MayaH]

Thank you all for the sound advices! After the oil change and 3000 miles put on the car, the rattling sound is gone and the idle hunting is pretty minor compared to what I had before.However, after I fix the coolant leak on my 2003 Z4, I’ll have the car checked for vacuum leak and faulty sensor.
As requested, here is my beauty: