When the variable cam sprocket went out on my 93 Nissan it sounded exactly like a knocking piston or rod. It had an internal spring in the sprocket that failed.

 

I was happy to learn it was not piston or rod related. The leak down test proved that. Actually, I was very surprised to find the leak down numbers so good. It's like a new motor.

Incidently, my cost for the vario cam solenoid valve was $260.00.

 

We started the car this morning and no noise. Five minutes into the warm up the noise returned. Did the replacement solenoid valve fail?

 

Sounds scary Chad. Hope everything is ok...

PS I've got your stuff here so swing by anytime

 

How big a difference would the regular 996 throttle body make in a 996 tt?

 

In a stock tt not much difference at all. In fact you probably would lose some torque.

 

The variocam sprocket may have failed. When they fail the inner and outer parts of the sprocket snap back and forth as the cam lobes open the valves. It can make a loud knock that varies with RPM and engine load. You may be able to hotwire the solenoid (or pull the wire off) so you can manually control the variocam and listen for a change in the knock.
A failed solenoid would leave the cam in the advanced or retarded position, but I don't see how it would make it knock.
An air bubble in the variocam chambers could cause a knock but there should be a small orfice to bleed off air.

 

The new tensioner arrived at a cost of $660. It will be installed on Monday. If this isn't it, then off to the cam sprocket and lifters.

 

The tensioner will not be installed until tomorrow. I started her up and the sound is a very slight tick, tick, tick coming from the driver's side bank. Hope to resolve this tomorrow. Other than the tick, she sounds great. Only 996tt that I have ever heard that shakes the ground a little at idle. The motor definitely has a loping sound at idle. Reminds me of the old radical cammed motors. For a 3.6 motor it is a little on the wild side.

 

Well, they were a day late installing the tensioner. I was surprised it has a 959 part number. The old one was spongy while the new one was stiff. Thought we had the problem solved until we started her up. Alas, the tick is still there.

We have changed the solenoid that changes the oil gallery on the vario cam and we have changed the cam tensioner. We have now ordered the solenoid that changes lifters from one cam lobe to the other on the vario cam. Should be able to check that out on Friday.

If that doesn't do it, then off to the cam sprocket and lifters.

 

The solenoid that changes the lifters on the cam lobes arrived late Friday. Monday it will be installed. Keeping my fingers crossed.

 

Same here can't wait too see her back in action!

 

We got the vario cam solenoid installed and started the motor. Not only was the "tick" still there, but now we had an oil leak between the motor and the tranny. We removed the tranny and discovered a "plug" was pressed out of the case. This is a plug that goes to an oil gallery.

We removed the oil filter and found metal on the magnet. Oh well, the motor now needs to be torn down. There is definitely a problem somewhere in the valve trane. Glade we caught it when we did.

 

it never ends does it. That's why I think when I do my next hot rod i'm gonna buy one already built

 

I'll take some pics of the problem once we locate it. I believe we have discovered the power/torque limits of the internally stock 3.6 motor.