Strange noise at 1500rpm. VQ25DET

[Darkmeat]

Got a bit of an issue.

2 days ago I noticed my motor is making a noticeable 'clackkk' sound at 1500rpm, under no load.

I only noticed it because I was standing beside the car, with the bonnet open, gently revving the motor.

The 'clackkk' sound comes from the top of the motor (not from the front under the cam chain cover) and occurs whether I stab the throttle or increase revs gradually. It happens as it passes through 1500rpm. It's predictable and repeatable.

I've never heard this sound while inside the car with the bonnet closed. So I don't know if it's happening while driving and/or with the engine under load.

I thought, since it happens only at 1500rpm, that it might be the CVCT system. But that is Continuously Variable. So I'm thinking there should be no single point or RPM value at which the VCT 'switches' the timing.

Car is an NM35 with VQ25DET, Hypergear turbo, all supporting cooling, exhaust, & fuel mods for 270kw atw, inc. lots of Scotty parts, and eManage Ultimate ECU.

Can anyone help me with knowledge, experience, diagnostic advice?

[West]

2 hours ago, Darkmeat said:

Got a bit of an issue.

2 days ago I noticed my motor is making a noticeable 'clackkk' sound at 1500rpm, under no load.

I only noticed it because I was standing beside the car, with the bonnet open, gently revving the motor.

The 'clackkk' sound comes from the top of the motor (not from the front under the cam chain cover) and occurs whether I stab the throttle or increase revs gradually. It happens as it passes through 1500rpm. It's predictable and repeatable.

I've never heard this sound while inside the car with the bonnet closed. So I don't know if it's happening while driving and/or with the engine under load.

I thought, since it happens only at 1500rpm, that it might be the CVCT system. But that is Continuously Variable. So I'm thinking there should be no single point or RPM value at which the VCT 'switches' the timing.

Car is an NM35 with VQ25DET, Hypergear turbo, all supporting cooling, exhaust, & fuel mods for 270kw atw, inc. lots of Scotty parts, and eManage Ultimate ECU.

Can anyone help me with knowledge, experience, diagnostic advice?

They do switch.

Sounds like your cam actuator is worn out or broken, have seen this issue on a few M35 lately. I believe Scotty can fix them without removing the engine.
Another member has his fixed at Chaser.

[Darkmeat]

On 8/3/2018 at 3:02 PM, West said:

They do switch.

Sounds like your cam actuator is worn out or broken, have seen this issue on a few M35 lately. I believe Scotty can fix them without removing the engine.
Another member has his fixed at Chaser.

Thanks for the info, West. Most appreciated.

Hope I can find someone in the Central Coast - Newcastle area who knows these motors.

[Old Gregg]

After sitting off the road for sometime I received my car (2001 ARX) back with a sound that fits the cam actuator problem - comes in at around 1600 rpm, up to about 2400. Starts after running for one or two minutes, marble in spray can/ clacking sound. When car was returned the oil was quite dark, run 5 /30 full synth. Oil and filter change, same full synth 5/30 oil. Sound still there after warm up. 

So this fits in with all of the postings re. it being cam actuator. Also note it tends to make the noise more often if accelerator is given little blips rather just pressed.

What I am not sure about is why the sound stays no matter which of the 2 blue plugs at the front of the engine that you disconnect and disconnecting these do not cause CEL to show on dash. (Might make it very slightly quieter if the driver side is disconnected.)

Inclined to think this means cam actuator/s are still the problem and are significantly damaged?

Worth trying 10/40 oil? 

Possible further damage trying to drive to a repairer?

[GTSBoy]

It's not because it's switching.....it's because it's mechanically f**ked, that it makes noise.

[Darkmeat]

On 8/11/2018 at 3:05 PM, Old Gregg said:

After sitting off the road for sometime I received my car (2001 ARX) back with a sound that fits the cam actuator problem - comes in at around 1600 rpm, up to about 2400. Starts after running for one or two minutes, marble in spray can/ clacking sound. When car was returned the oil was quite dark, run 5 /30 full synth. Oil and filter change, same full synth 5/30 oil. Sound still there after warm up. 

So this fits in with all of the postings re. it being cam actuator. Also note it tends to make the noise more often if accelerator is given little blips rather just pressed.

What I am not sure about is why the sound stays no matter which of the 2 blue plugs at the front of the engine that you disconnect and disconnecting these do not cause CEL to show on dash. (Might make it very slightly quieter if the driver side is disconnected.)

Inclined to think this means cam actuator/s are still the problem and are significantly damaged?

Worth trying 10/40 oil? 

Possible further damage trying to drive to a repairer?

Errm. You lost me at "two blue plugs at the front of the engine ..."

What two bue plugs?

ta.

[Old Gregg]

On ‎8‎/‎14‎/‎2018 at 12:06 PM, Darkmeat said:

Errm. You lost me at "two blue plugs at the front of the engine ..."

What two bue plugs?

ta.

There is blue connector on left and right bank at the front of the engine. Apparently they are the electrical connector for the VVT cam actuator. (These seem to be given a few different names on here.)

These two links might help. Check on the above info as I was posting on here to try to understand exactly how these behave rather than offer advice.

Good Luck.

Following discussions are some help:

 

[Darkmeat]

On 8/11/2018 at 4:21 PM, GTSBoy said:

It's not because it's switching.....it's because it's mechanically f**ked, that it makes noise.

I'm mechanically f**ked and I don't make a noise like that.

[BoostdR]

The EVTC activates at 2.5volt output from the MAF sensor. You can control the activation point by manipulating the MAF signal. Don’t forget to fix the fueling if you do. Also the trans shift timing will be affected with any modification of MAF output.

Matt