This has happened the past two mornings, on my 05 6MT sedan. For about the first five minutes of driving, I start to hear some kind of revving noise under the hood. Not the engine, but maybe an electric motor somewhere? It happens as I give it juice (in lower gears). Not extremely loud, but loud enough to hear over the radio. I flipped off the air conditioning, that wasn't it. Maybe the fan? Performance doesn't seem to be affected at all. Outside temperatures in the morning are average (60s).

It almost seems like this is something the car would do while getting warmed up, but it never did it before.

After a few minutes, it disappears.

Any ideas?

I'll take it in the shop, but I imagine that by the time I get there, it will be gone.

Thanks!

 

Does it only happen when in gear? I would pop the hood and pinpoint the noise location. Check the fans to see if they are spinning.

 

Thanks. Only happens when I am moving (so can't look under the hood) and only for the first few minutes. I know this is odd, I have no idea how to demonstrate it to the Infiniti Service Department.

 

Does the noise go up and down with the motor's revs? Does the noise stay at the same rev level? Or does it pitch up and down independent of the motor?

 

Does it sound like your electric fans after you are idling in traffic?

 

Yes, it sounds like a fan.

What I've noticed over the past couple days - it happens when RPMs get to about 2500 to 3000, then it disappears (unless I can't hear it over the RPMs). It doesn't do it in idle. It starts occurring as the RPMs increase, but it doesn't go down with them. It may be temperature related (it's more predominant in the morning after the car has been sitting in the garage).

I have an appointment next week to get it checked out.

 

If it's temperature related, I would guess that is a drive belt issue. Do you have any glazing on the belts or a loose tensioner?

Can you pinpoint the location of the noise? If is in the center of the front of the motor, it could be the water pump as well.

Good luck.

 

I had a similar issue with my old I35. It was actually an electronic engine mount. It was trying to level out the engine but could not and you could hear it make a rev noise at a particular rpm.