Need help to diagnose engine rattle/knock

[benger]

Hi,

I'm a new Norwegian user to this forum after countless of hours trying to understand the Fairlady and the VG30DETT engine. I do have a lot plans to do with this car, but first, the engine must run perfect!

My car is a 90' 300ZX TT with 90.000 miles on the block. I bought the car with a vibration in the engine. It should only be a injector...

Now I have done the following:
* Series 2 PTU
* 6 JECS 370cc injectors
* OEM spark plugs
* Valve cover gaskets
* Plenum intake gasket
* PCV hoses
* Coil pack and injector connectors

Balance tested, no dead cylinders.

Previous owner did a timing belt replacement, but I don't know if he did a complete service with idler pulleys, cam spring and seals etc. Ignition timing is set and measured to 15 BTDC. Compression test turned out within spec. But still, the car doesn't feel like a smooth V6. A little constant vibration at idle. Vibration increases at higher RPM's with a rattle/knocking noise at around 3000 RPM. VTC related? See video

What could be the cause of this issue? Timing belt off with a tooth, cam gear/VTC? I'm stuck

https://www.youtube.com/watch?v=URLHbwH ... e=youtu.be
https://www.youtube.com/watch?v=ZzIRlEW ... e=youtu.be

This is how my engine looks atm:

[Ziggy1621]

Welcome to Nico! Sounds like you're treating her right! I'm on my phone, so I can't look up a good article on it, but what it sounds to me is the infamous VTC rattle. Look that up

[ThisIsSparTTa]

Does it only do it as you change throttle rapidly? Can you just hold at an RPM or slowly ramp up?

Try unplugging the VTC solenoid's and see if it goes away.

That's not rod knock, but it is bizarre sounding.

Another random question, are you using 91+ Octane fuel?

[benger]

The "knock" appears only when I change the throttle rapidly between 2500-3500 RPM. If I keep the engine steady at 3000RPM, the noise disappears. At idle, the engine does have a weak vibration. As mentioned, the vibration gets stronger when the knocking/rattle sound appears at around 3000 RPM. Is it possible that a bad VTC cam gear can result in engine vibrations?

I have ordered Conzult do some more analyzing.