N18 Weird Noise and Hesitation, No Codes?
 

I posted this under "Stock Problems/Issues" but hadn't gotten any responses... Maybe you all can help!

My 2013 R56 S has been making this very loud valvetrain-esque noise when the engine isn't up to temp yet (still in warmup sequence) and only when using light throttle, like when leaving my neighborhood. If I keep the car below 2k RPM it never happens. 2.5K RPM it starts to happen. I never take my car above 3k RPM until it's warm.

To describe the sound, it's like a loud knocking/rattling that gradually becomes louder over a second or two. If I give the car more gas (about half throttle), it goes away. It never happens when the car is warmed up, and it never throws a code (UGH). There is a very slight hesitation when I hear the noise.

I attached a sound clip, which isn't the best example as it's a bit hard to hear the difference. In-person it's quite pronounced and very easily audible from outside the car. The noise comes in around the 5 second mark and stops when I let off the gas at around 10 seconds. To me, it seems possibly VANOS related like as if the camshaft goes out of time? Maybe it's fuel pump related?

I already had to replace my intake vanos solenoid due to a CEL but did not replace the exhaust side. The intake vanos solenoid was sparkling clean when I replaced it, so I figured it wasn't due to residue build-up and didn't think to replace the exhaust side, too.

Yes, the car has always been topped up with oil https://www.northamericanmotoring.co...lies/smile.gif Just thought I'd mention that... And it runs great once warm.

Has anyone else had this happen with their N18? Any ideas?

Nathan - Were you able to fix the noise?

I have same issue, sounds like an exhaust leak during light throttle during warm-up. I can't get it to exhibit this any other time. I found the exhaust bellows failing & replaced that, but I think that may be an effect & not a cause. (still has problem)

Engine runs perfectly otherwise.

BTW i have N16 engine (NA) with 50K miles.

Edit - Another clue the noise will suddenly stop, like something grabs or lets go.

I am going to clean Vanos solenoid next.

Thank you & others for any clues to help fix this