Weird Noise Around 1500rpm

[STLKHR]

Hi guys this one seem's like a hard problem to find!

At idle there is a rubbing sound noise (rubbing is the best description i can come up with) it take the revs up just past 1500rpm, it then goe's away! i rev up to 4000rpm and take my foot off and around 1500 rpm it will hesitate before dropping to idle 900 rpm, as soon as it hits 1500rpm the rubbing/grinding noise comes back.

Now i was thinking is it like a belt that sort of comes right when you get to a certain rpm (like an unbalanced wheel, you drive through the unbalanced point), but then i was thinking why does the motor hesitate right at the point it starts making the noise?

Has it got something to do with the VCT?

Anyone had this prob or got any ideas? cheers

[r32na]

it is a misfire? or just a weird noise and a rumble?

[mad082]

is it like a rubbing noise or could it be a vibration in a belt? the reason i ask is that it may possibly be a pulley bearing causing a vibration in a belt when at a certain speed. an example of this is a semi common problem with SSS pulsars where the aircon belt vibrates at idle when the aircon is on and the moment you blip the throttle it goes away. new bearings in the pulley seems to solve it for a little while.

other possilbe causes could be air in the power steering pump (or just low fluid) but that will generally be all the time and get louder as you turn the steering.

the revs dropping to 1500 then down to idle is pretty normal as well. i have owned lots of cars that do that.

[R34 -_-]

How loud is it? my car also hesitates before dropping to idle sometimes but it doesn't make any weird noises

Edited September 22, 2009 by R34 -_-

[STLKHR]

How loud is it? my car also hesitates before dropping to idle sometimes but it doesn't make any weird noises

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Hey guys, im picking it must be a belt then i just thought it weird due to the revs hesitating at the point it starts rumbling, does not miss at all. will check my cambelt as i am picking its that, may just take a belt of at at time to slowy eliminate each possible prob.... so allot of cars hesitate for half to a whole sec around 1500rpm when throttle is released? weird..

cheers

[R34 -_-]

when the revs go down sometimes it blips up a tiny bit before going to flat idle. But i would say that's to do with the acc valve and vvt etc.

Edited September 23, 2009 by R34 -_-