A couple of weeks back my 06 350Z (UK Rev-up 300bhp) started making a metallic tapping at idle. The car was with a 350Z specialist for a couple of weeks and no one could find the issue. I've collected the car now but I'm at a complete loss what to do with it. They've told me the only thing I can do is to just keep driving it to see if the issue progresses and becomes easier to pinpoint.

• Using a stethoscope the issue is loudest on the passenger bank, around cylinder 1 near the head.
• Noise is intermittent, only happens when hot but not always and can dissipate while running for no reason or when switching the engine off
• Noise raises with RPM but hard to hear at higher RPM
• Clutch in doesn't change the noise
• Tested for rod-knock
• Fuel damper has been changed
• Timing chain tensioner checked through inspection hatch, secondary chain also
• VTC solenoid unplugged on passenger bank, noise doesn't change
• Loading up the engine against the handbrake dissipates the noise
• Flywheel looks ok
• Disabling cylinders in turn on passenger bank doesn't change the noise
• Cam looks fine with no visible wear
• Bores examined with borescope, look fine but piston 1 is oddly clean with no carbon buildup
• Valve clearances are perfect
• Oil pressure is very good

The videos do somewhat exaggerate the noise. There is a slight irregularity about the tap.

I've owned the car for about 11k miles. It used a small amount of oil when I first got it. I first serviced it with Fuchs Titan 5W30 and it went nearly 9K without using a drop. The car rarely gets driven hard and gets an oil change every 4.5K. The fans failed not long after I got it and briefly overheated, not much coolant lost, but that's the only engine related issue it's had.

To be honest, I can't even tell what is or isn't abnormal sound now! It's starting to drive me a little crazy to say the least.

 

Car can start off cold, sounding fairly normal. Bring it up to temp slowly with normal driving, tapping starts. A few runs of high revs and it's seemingly back to sounding normal again.

Oil pressures

85psi on first start
32psi when up to normal temp
25psi about 10mins of sedate driving later

All above at idle

60psi at 2500rpms

 

Almost certainly the noise is gone by the time you reach down to about 25psi (i.e hot). Going to disconnect both VCT solenoids.

 

Disconnecting the VCT solenoids didn't help.

 

Sounds like valve/tappet noise - but there is not much to go wrong there - I would fear a valve Colette has escaped

 

That was my initial thought, but the fact it starts off quiet, begins to tap as it warms up, and then disappears (or at least is much, much quieter) when it gets even hotter confuses me.