Jump to content
SAU Community

Recommended Posts


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?

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/474637-strange-noise-at-1500rpm-vq25det/
Share on other sites

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.

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.

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?

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.

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:

 

  • Thanks 1
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.

  • Haha 2
  • 4 weeks later...

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

  • Thanks 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Actually, that's not entirely true. It's also the same motor in the 1st gen Nissan Cube but they're rare as hen's teeth.  
    • Yeah it is always worth testing and balancing actuators out of the box, just set the pressure regulator on a compressor very low (eg 5 psi) and increase it slowly to see when they both move.....unfortunately while you may be able to adjust the length of the actuator rod to minimise any difference, the actual pressure they move from is not adjustable so you need a well matched pair. And yes, the VCAM is probably contributing; the earlier in the rev range they come on boost and the slower the revs build (I think your demo was in 5th), the more you notice it.  Driving at WOT through 1st, 2nd, 3rd etc you will probably never hear it as any shuffling starts and is over super quickly
    • oh they were with that motor, you need to remove the engine to change the spark plugs (don't have to, but it does make it easier)
    • I certainly fall into the annoyed camp, but glad to hear that if it's happening at low boost then I'm not likely going to blow a turbo and end up with metal shards in my oil. Just feels like it prevents me from really driving it without hesitation and "peak" performance. Wonder if it's the VCAM, it did an impressive job of shifting the torque curve and faster spool, but maybe now it's "too fast" and there's too much air for how open the throttle is.  Based on some other threads, will also do some reading on synchronizing the actuators. They are the default actuators that come on the Garrett's and I would think they would be set the same coming from the factory, but if the turbos don't actually work exactly the same way at the same time as previously mentioned, it would be worth making sure the actuators are actuating together properly
    • I went down this rabbit hole before, ended up sourcing a motor from the UK (I'm in Japan) which also didn't function correctly. With the original motor, I disassembled it and reassembled it and it works somewhat, sometimes. What I could deduce from all my screwing around is that there is calibration of the gears on the inside of the motor and two ramps on the main gear which activate switches that operate the motor and move the sunroof either to retract into the roof or tilt. Where I got stuck was that, it seemed in my case that one or both of the switches that are activated by the ramp on the gear did not always activate and thus the motor did not move, causing it to sometimes not retract or tilt (apologies, I've forgotten which way it didn't work.).  Of course this part is discontinued at Nissan now, it's the same part in the S15 but no other models. I also contacted the manufacturer of the component for schematics - forgot the name, they're based in Gifu - but they declined to share the information due to being bound by an NDA, sadly. Looking through my pictures now, it seems I last had a crack at this in 2022. See, I so kindly wrote "open" and "close" next to the switches. If you figure it out, please do tell me. Those little switches, with the red buttons may need to be replaced.
×
×
  • Create New...