Resonation in the car above 4k's

[Mitco39]

Hi guys,

The car recently developed (right around the time I did an oil change, not sure if it is just a coincidence or not) a resonation through the whole interior when off the throttle and above 4000 rpms. Its most noticeable when you are slowing down a bit aggressively and downshifting to about 5-6000 rpm. I have spent the better part of the weekend going over everything with no luck.

It also doesn't seem to start right away, I have to drive the car for a couple miles before it decides to do its thing. You cannot hear it from outside the car (had a buddy check beside me on the road) which points towards something rubbing somewhere possibly.

I spent a couple hours under the car last night looking for anything that could be rubbing with no luck. Has anyone ever had an idler wheel go out on the belt?

The fact that it resonates makes it very hard to determine where the sound is coming from. It does appear to follow the rpms. Maybe an engine mount? How would one tell if one of those let go? Since it only happens on decel (atleast from what I can hear, the car gets pretty loud excelerating) it could be a mount on drivers side I guess. But this wouldnt explain it not doing it right when I start driving it.

Just looking to see if anyone has experienced this on their Z's.


Thanks guys,

Mitch

[edconline]

I dont remember noticing anything on the last cruise.. How loud is it from outside the car? I'm surprised you can hear any vibration that isn't coming from the sub!

[fuct]

coming from an inline 6, i think these V6's are just rough vibration making machines. almost feels like my dads crummy ford ranger V6. :/

[Mitco39]

Originally Posted by edconline

I dont remember noticing anything on the last cruise.. How loud is it from outside the car? I'm surprised you can hear any vibration that isn't coming from the sub!

You can't hear it from outside the car, its just the right frequency where it resonates in the cab. If you open the windows you can hardly hear it. After making that post I thought a bit more about it and I remembered I moved the aftermarket oil pressure sending unit to get to the oil lines (had a leak). I bet you its rubbing on my roll bar now. It would explain me only having it on decel as the roll bar would roll up into the engine bay even more. I am going to pull it off tonight and look for wear marks.

It however does not explain why I dont hear it right when starting to drive the car.

You would be surprised, unless I am on the highway the stereo stays quiet. I love the car sound when driving around the city. BecauseRaceCar right? haha

[binary0x01]

I notice the stick vibration in the same manor. Dunno what's up but an Aluminium V6 VHR motor can be used as an excuse I guess heh.

[Mitco39]

If I was to just get in the car after never driving one I probably wouldnt think otherwise. But its the fact that it recently developed that leads me to believe its something unrelated to the construction of the engine.

I am pretty picky when it comes to odd noises, hell I have to pull over to pick rocks out of my tires. haha

[fuct]

Originally Posted by Mitco39

If I was to just get in the car after never driving one I probably wouldnt think otherwise. But its the fact that it recently developed that leads me to believe its something unrelated to the construction of the engine.

I am pretty picky when it comes to odd noises, hell I have to pull over to pick rocks out of my tires. haha

same here! im always worried its a nail!

[Mitco39]

Sooooooo No rubbing where I expected.. But I did find this. Seems weird considering all the pulleys are smooth and I went over the whole belt, nothing is rubbing on it. Anyone seen this before?

[Mitco39]

Starting to lean towards a idler pulley. Maybe? Maybe not? haha Could make sense, although any ones i've heard of failing are usually audible outside the car.

[AlexRaymond19]

Is this a rattle, or a resonation? I get a weird rattling noise around the same rpm, checked everything and can't find where its coming from. Its stupid annoying, and just started happening one day

[Mitco39]

If I was to compare it something it would be standing close to a bees nest and hearing that hum.

I know the feeling AlexRaymond, its to the point where i'll take the truck just so it doesn't drive me crazy. Maybe check your heat shields to make sure none of them are lose? That is if you have more of a rattle than a resonation.