Unnerving mystery vibration noise - Details and sound file inside
04-04-2011, 03:30 PM
#1
Unnerving mystery vibration noise - Details and sound file inside
OK Detectives, got a mystery here.
The car is a 2001 I30, the Maxima's snobby twin, with 74k miles.
I've noticed a very strange rattling noise but I have not been able to narrow down exactly where the noise is coming from. I've tried to pull over quickly when it's making the noise and listen but it goes away too quickly. This weekend I intend to have a friend drive the car as I climb around and try to find the noise.
Here is a recording of the noise. I had to throw a still picture on there or youtube wouldn't let me upload -- so ignore the gauges, etc for hints.
http://youtu.be/Nqu6WM16wbA
The noise usually happens in the mornings - at first only when it was below freezing, however it's been happening at gradually warmer temperatures as time goes on. It used to go away once the car had been moving for a while, but today it sang for a full 10-minute ride. Sometimes the noise goes away for a few weeks, then comes back.
It doesn't matter if I am in gear or not, moving or stopped.
The noise is always the same pitch as you hear it here -- it does not vary based on RPM, Vehicle Speed, or Wheel Speed. This recording was taken in my garage with the microphone held under the driver's door.
The noise is not linked to any specific RPM (like heat shields which tend to vibrate at exactly 1200 RPM, etc) however it seems to appear randomly between high idle and about 1500 RPM. I've dealt with exhaust-related noises on other cars and I'm convinced it's something else.
The car is not performing badly in any way, nor are there any codes thrown.
My instinct tells me that it is an electric motor of some sort because of the constant speed, but beyond that I"m lost.
Any ideas?
The car is a 2001 I30, the Maxima's snobby twin, with 74k miles.
I've noticed a very strange rattling noise but I have not been able to narrow down exactly where the noise is coming from. I've tried to pull over quickly when it's making the noise and listen but it goes away too quickly. This weekend I intend to have a friend drive the car as I climb around and try to find the noise.
Here is a recording of the noise. I had to throw a still picture on there or youtube wouldn't let me upload -- so ignore the gauges, etc for hints.
http://youtu.be/Nqu6WM16wbA
The noise usually happens in the mornings - at first only when it was below freezing, however it's been happening at gradually warmer temperatures as time goes on. It used to go away once the car had been moving for a while, but today it sang for a full 10-minute ride. Sometimes the noise goes away for a few weeks, then comes back.
It doesn't matter if I am in gear or not, moving or stopped.
The noise is always the same pitch as you hear it here -- it does not vary based on RPM, Vehicle Speed, or Wheel Speed. This recording was taken in my garage with the microphone held under the driver's door.
The noise is not linked to any specific RPM (like heat shields which tend to vibrate at exactly 1200 RPM, etc) however it seems to appear randomly between high idle and about 1500 RPM. I've dealt with exhaust-related noises on other cars and I'm convinced it's something else.
The car is not performing badly in any way, nor are there any codes thrown.
My instinct tells me that it is an electric motor of some sort because of the constant speed, but beyond that I"m lost.
Any ideas?
Last edited by Montego Murph; 12-14-2011 at 09:19 AM. Reason: changed link to video
04-04-2011, 10:34 PM
#2
Check the engine fans given the symptoms I suspect the fan that gets kicked on when your defroster is going (Defrost cycle kicks on the A/C to dehumidify the system) has a broken motor mount or the shroud is cracked. Inspect your radiator fans for any cracking of the motor mount spokes and any rub marks on the housing itself, also check the blades themselves for any cracking or broken blades.
04-05-2011, 04:35 PM
#3
Check the engine fans given the symptoms I suspect the fan that gets kicked on when your defroster is going (Defrost cycle kicks on the A/C to dehumidify the system) has a broken motor mount or the shroud is cracked. Inspect your radiator fans for any cracking of the motor mount spokes and any rub marks on the housing itself, also check the blades themselves for any cracking or broken blades.
I'll give this one a check by hand later on with the engine cold and off. This morning I started it up and made sure to turn the defroster on, but no noise.
Baffling!
04-15-2011, 03:59 PM
#4
OK... It wasn't anything radiator/fan related.
Today it made the noise all the way to work. Now that I had a longer window of observation, I learned the following:
The noise appears loudest between 1200 and 1700 RPM. I believe it is a resonant vibration of some sort.
The car must be "under load" to make the noise. Sometimes it will do it upon just starting up, but today I pulled over into a parking lot and idled the engine at various rpms with the door open in hopes of at least determining WHERE the noise was coming from. No luck. However, when I put the car in Drive, set the brake and foot brake, I could rev the engine a bit and make it happen at 1500 RPM. (Don't worry, I did not do it for more than a second or two. Don't want to burn up the tranny.)
Today I got under the car and looked for ANYTHING that can rattle. Some of the air dam bolts in the front are missing -- the heads broke off at some point. I slapped those around but they didn't seem to make the noise
What sort of electric pumps and motors do we have on this car that I should check?
Fuel pump I know is one.
Anything ABS related?
Today it made the noise all the way to work. Now that I had a longer window of observation, I learned the following:
The noise appears loudest between 1200 and 1700 RPM. I believe it is a resonant vibration of some sort.
The car must be "under load" to make the noise. Sometimes it will do it upon just starting up, but today I pulled over into a parking lot and idled the engine at various rpms with the door open in hopes of at least determining WHERE the noise was coming from. No luck. However, when I put the car in Drive, set the brake and foot brake, I could rev the engine a bit and make it happen at 1500 RPM. (Don't worry, I did not do it for more than a second or two. Don't want to burn up the tranny.)
Today I got under the car and looked for ANYTHING that can rattle. Some of the air dam bolts in the front are missing -- the heads broke off at some point. I slapped those around but they didn't seem to make the noise
What sort of electric pumps and motors do we have on this car that I should check?
Fuel pump I know is one.
Anything ABS related?
05-06-2011, 05:46 AM
#5
MYSTERY SOLVED. (or so I thought -- this was purely coincidental or magic)
I jacked up the car, put it on stands, and crawled underneath and just LOOKED.
Trying to find anything that COULD make noise, anything that might have a motor, a valve, anything.
Turns out it was my flex pipe -- the part of the exhaust made of braided material. It had broken apart from its mount on the front half and was rattling on the metal accordion tube inside.
For experimental purposes I got a hose clamp and tightened it down on the loose part as far as it would go. Drove 1,900 miles in 2 weeks and didn't hear a peep.
So... There we go.
I jacked up the car, put it on stands, and crawled underneath and just LOOKED.
Trying to find anything that COULD make noise, anything that might have a motor, a valve, anything.
Turns out it was my flex pipe -- the part of the exhaust made of braided material. It had broken apart from its mount on the front half and was rattling on the metal accordion tube inside.
For experimental purposes I got a hose clamp and tightened it down on the loose part as far as it would go. Drove 1,900 miles in 2 weeks and didn't hear a peep.
So... There we go.
Last edited by Montego Murph; 12-14-2011 at 07:15 AM. Reason: Corrected the "mystery solved" line
12-13-2011, 04:06 PM
#7
Well this is strange.
The noise is back, but my follow-up in post #5 has NOTHING to do with it. Somehow that was just a coincidence that when I put the hose clamp on the flex pipe, the weather must have warmed up enough to not do it any more.
Now we have a new question which I will reveal in a second...
As I was leaving work today, I put the key in the ignition and started to turn it. I stopped mid-turn as I had one of those "mental checklist" moments -- did I remember to do that one thing my boss asked me to do.... I had the key held halfway between "run" and "start" -- far enough to turn off all the electronics in the cabin (hvac, dash cluster, radio) but not far enough to engage the starter.
Then I heard it. That fluttering rattling noise, coming from the same mystery location.
So now the new question is: When the ignition is in "starting" mode and all extraneous electrical loads are shut off, what still remains energized?
Let us open our hymnals to the SC chapter....
Fuel Pump. Plausible. This noise does seem to come from around the resonator, which is more or less below the fuel pump.
However, why would the fuel pump only vibrate like this http://youtu.be/Nqu6WM16wbA for the first few blocks of driving? Wouldn't it be a perpetual thing whenever the pump is running?
What else would run during "start" mode?
The noise is back, but my follow-up in post #5 has NOTHING to do with it. Somehow that was just a coincidence that when I put the hose clamp on the flex pipe, the weather must have warmed up enough to not do it any more.
Now we have a new question which I will reveal in a second...
As I was leaving work today, I put the key in the ignition and started to turn it. I stopped mid-turn as I had one of those "mental checklist" moments -- did I remember to do that one thing my boss asked me to do.... I had the key held halfway between "run" and "start" -- far enough to turn off all the electronics in the cabin (hvac, dash cluster, radio) but not far enough to engage the starter.
Then I heard it. That fluttering rattling noise, coming from the same mystery location.
So now the new question is: When the ignition is in "starting" mode and all extraneous electrical loads are shut off, what still remains energized?
Let us open our hymnals to the SC chapter....
Fuel Pump. Plausible. This noise does seem to come from around the resonator, which is more or less below the fuel pump.
However, why would the fuel pump only vibrate like this http://youtu.be/Nqu6WM16wbA for the first few blocks of driving? Wouldn't it be a perpetual thing whenever the pump is running?
What else would run during "start" mode?
12-14-2011, 06:03 AM
#8
Today's observation:
I removed the rear seat before leaving for work to see if the source of the noise would be obvious.
I'm not completely convinced that it's the fuel pump. The pump still made its "whirrr" noises like any car would -- however when I did the "hold the key just before the starter kicks on" thing like yesterday, I got the fwap-fwap-fwap noise in addition to the pump whirring noise.
I read through the "SC" section of the FSM last night but could not find anything about a priming pump or some other device that is triggered by the start circuit. I could have missed something though as I'm not 100% skilled at reading electronic diagrams.
The motor mounts have been disconnected and isolated, so I know it's not that. It isn't a "servo" noise either, so it's not the IACV.
I just remembered this... about a month or two ago, when I first turned the key to "run" before hitting the starter, there would be a flatuent "vvwwwooooop!" noise coming from somewhere, but I never could quite place where it came from. I'm betting these incidents are related.
Any ideas?
I removed the rear seat before leaving for work to see if the source of the noise would be obvious.
I'm not completely convinced that it's the fuel pump. The pump still made its "whirrr" noises like any car would -- however when I did the "hold the key just before the starter kicks on" thing like yesterday, I got the fwap-fwap-fwap noise in addition to the pump whirring noise.
I read through the "SC" section of the FSM last night but could not find anything about a priming pump or some other device that is triggered by the start circuit. I could have missed something though as I'm not 100% skilled at reading electronic diagrams.
The motor mounts have been disconnected and isolated, so I know it's not that. It isn't a "servo" noise either, so it's not the IACV.
I just remembered this... about a month or two ago, when I first turned the key to "run" before hitting the starter, there would be a flatuent "vvwwwooooop!" noise coming from somewhere, but I never could quite place where it came from. I'm betting these incidents are related.
Any ideas?
Last edited by Montego Murph; 12-14-2011 at 09:22 AM.
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