[n55demon]

Hey guys, ive been noticing that my car has been making a weird noise around 800-1000 rpm. I figured it might be a belt issue or something, and saw today that my idler pulley seems to be vibrating. sound is only coming from those specific rpms 800-1000, making like a krrrrrrrrrrrrrr noise or like if something was grinding noise. noticed that my idle has been a little funky lately also, and i figured maybe it was related to this or something. sometimes my rpms jump from 600 to 800 then back down after a blip in throttle. looking to replace the tensioner, anyone know if this will fix my issues?

youtube video of my tensioner pully: https://www.youtube.com/shorts/0RCg7TqWzqw

[thejeremyman9]

Some amount of jiggle is unavoidable. However if you are over 60k or so miles its probably worth getting the kit with the belt from FCP and swapping it out preventatively. Mine looked similar and BMW replaced it under CPO warranty.

Having said that it would not affect idle.

[n55demon]

Originally Posted by thejeremyman9

Some amount of jiggle is unavoidable. However if you are over 60k or so miles its probably worth getting the kit with the belt from FCP and swapping it out preventatively. Mine looked similar and BMW replaced it under CPO warranty.

Having said that it would not affect idle.

yeah im at 81k right now.

[n55demon]

Originally Posted by thejeremyman9

Some amount of jiggle is unavoidable. However if you are over 60k or so miles its probably worth getting the kit with the belt from FCP and swapping it out preventatively. Mine looked similar and BMW replaced it under CPO warranty.

Having said that it would not affect idle.

Sometiems during city driving in like nyc, itll idle a littler bit higher, but i dont know if that could be caused by heat issues or just having heat on high etc. ive noticed during the summer when i had my ac on my car would idle a bit higher as well.

[thejeremyman9]

Originally Posted by n55demon

Sometiems during city driving in like nyc, itll idle a littler bit higher, but i dont know if that could be caused by heat issues or just having heat on high etc. ive noticed during the summer when i had my ac on my car would idle a bit higher as well.

Changes in idle based on AC load etc are normal, but fluctuations/bouncing up and down for no reason are not. So it just depends on what you are experiencing. Sounds like doing the belt/tensioner is not a bad idea, and see if it solves the problem.

[n55demon]

Originally Posted by thejeremyman9

Changes in idle based on AC load etc are normal, but fluctuations/bouncing up and down for no reason are not. So it just depends on what you are experiencing. Sounds like doing the belt/tensioner is not a bad idea, and see if it solves the problem.

you can hear a slight howl in the video if you listen closely. the sound kinda like a howl starts near 800 rpm and hold right at 1k then sounds normal. any idea? i still think it may be the tensioner.

[thejeremyman9]

Howl and idle issues can be signs of the VC leak IIRC. There are some similar threads on it where people think its their belt/tensioner and it ends up being the VC and howling air sound.

[n55demon]

Originally Posted by thejeremyman9

Howl and idle issues can be signs of the VC leak IIRC. There are some similar threads on it where people think its their belt/tensioner and it ends up being the VC and howling air sound.

i just fixed a boost leak today, and my car seems to be idling fine now! when installing the intake i had to plug the extra hole near the maf censor on the cts turbo intake. i capped it but i never put a hose clamp on it. got one today, car feels so much better, and pulls a lot harder as well. the howling sound is still there tho. whats strange to me is that it only makes the howling sound around the 1k rpm and never above it or below it.

[n55demon]

Originally Posted by thejeremyman9

Howl and idle issues can be signs of the VC leak IIRC. There are some similar threads on it where people think its their belt/tensioner and it ends up being the VC and howling air sound.

found this video:

definetly not experinecing this form of sound, i think its most noticeable on the inside of the car, took it to a mechanic hood open and he couldn't really locate the issue aside from the pulley looking loose and it only being on throttle at 1000 rpm then goes away instantly after going over or going under.

[F32Fleet]

Typically you'll hear a rattling sound which will increase with engine speed. This is because the grease around the bearings of the pulley has dried out. Belt tensioners will have a little wobble. It's never dead still. Never.

Hearing a chirp can be another sign of a bad pulley or tensioner.


Try searching some YT videos.

[n55demon]

Originally Posted by F32Fleet

Typically you'll hear a rattling sound which will increase with engine speed. This is because the grease around the bearings of the pulley has dried out. Belt tensioners will have a little wobble. It's never dead still. Never.

Hearing a chirp can be another sign of a bad pulley or tensioner.


Try searching some YT videos.

my best friend has an n55, and i sent him the video of the sound. he said he experiences the same noise because of the cts turbo intake. guessing its just air reciruclating into the atmo, which was my first thought as well.