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Strange noise - diagnosis help please

Joined
30 January 2005
Messages
4,089
Location
Sarasota, FL
I was driving home from Miami on Sunday morning. It was a rainy day and I was taking the back roads (no interstate highways) for the 240-ish trip. Somewhere around half-way home, I started noticing a new noise. It was a faint popping sound that I could hear as I accelerated, but which would go away once I was cruising along, no longer putting a load on the drivetrain. The noise was rhythmic and grew faster with engine speed, not car speed.

Anyway, as I drove it became louder. By the time I got home it was a truly disturbing sound. The whole time the car seems to be running fine except for the noise. It seemed to be coming from behind me on the passenger side. At low RPMs as I accelerate it goes POP repeatedly until it's almost like a machine gun. It sort of sounded like a bad CV joint in some car I had in the past, but the frequency goes with the engine speed.

I got up Monday morning with the plan to drive it to my mechanic (about 2 miles away) and leave it. But now I had a whole new problem. No noise. None. He's had the car 2 days now and doesn't know what the noise was. He's driven it enough to get everything to operating temps, but nothing.

I need to go back to Miami this coming Sunday and sure would rather take my NSX, but not if we can't figure out what the hell the noise was. Any suggestions?
 
Your tires are worn to the point pieces of the tires are flapping the fender?


Frequency is based on the engine speed so it can't be the tires. Could it be your alternator or something with the belts? Location you describe puts it in the right spot.
 
I'm kicking myself for not thinking to pull out my phone and get some video/audio for my mechanic while it was happening. He's looking at the transmission today.

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Transmission oil was clean as could be, he's had the car two days with no noise. I'm taking tomorrow off work and going for a long drive to see if I can get it to happen again. Is there any way the rain I was driving in contributed to this?
 
Frequency is based on the engine speed so it can't be the tires. Could it be your alternator or something with the belts? Location you describe puts it in the right spot.

Supercharger belt after driving in the rain for an hour?

Grasping at straws here, I don't know what a slipping supercharger belt might sound like. The car didn't feel down on power although once I heard the odd noise I didn't get on it very hard.
 
I'm taking tomorrow off work and going for a long drive to see if I can get it to happen again.

Sorry I can't contribute to this thread, but I did want to point out that THIS is a committed NSX owner. :biggrin:
 
Out there--- but could be exhaust related close to engine


1) There are 2 8" EGR pipes high up in engine just under heads, one of mine cracked
2) or farther out idea: is it a turbo? if so waste-gate?
 
Sorry I can't contribute to this thread, but I did want to point out that THIS is a committed NSX owner. :biggrin:

On second thought, maybe I can actually contribute.

Check for a loose spark plug. It would sound like a ticking noise, and it would be once per revolution. This also makes sense since the hotter everything gets, the more it expands, hence the plug would get looser as the head got hotter, when it would compress back down and conceivably be tight enough to not make the noise next morning when cold.

It's a longshot, but it's something you do want to look at soon. A loose plug almost always works its way out and blows the threads in the head, so you won't want to deal with that.

Also check for a broken or cracked plug.
 
I will ask my mechanic today about spark plugs.

I took it for a 150 mile cruise in the countryside yesterday afternoon, and it ran perfectly. I tried to put on a good combination of cruise control driving plus a generous number of hard pulls and it was flawless. Barring new developments, I'm driving it to Miami on Sunday to pick my wife up at the cruise port. We might come home in a AAA tow truck or a rental car, but I gotta know what my car will do when I drive away in it.

My totally uninformed opinion at this point is that it's *got* to be related to the rain I was driving in. Rainy days aren't common this time of year, it might be a while before I can repeat those conditions.
 
So I drove it to the port of Miami and back today, a total just shy of 500 miles, and it ran perfectly and made no unusual noises.

I think the test will be the next time I have a chance to drive more than a couple miles in the rain.
 
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I'm sure it's because she's green...
I'm green, and I've been trying to pass emissions for a while now...
So, while I had her up replacing the O2 sensors for my next round with the Az Dept of Air Quality, I decided to put on new rotors, Red SS brake lines and red-out the calipers...makes sense, right?
 
It finally happened again! Almost 3 months have gone by and not a peep of the strange noise until this morning. I was at the end of my drive to work, about 9 miles @ 40-ish mph most of the way. I was accelerating away from a stop sign and I heard it faintly so I drove around some more and it got louder. This time I remembered to use my phone to get some audio. Here it is.

https://vimeo.com/118642399

You'll hear it most all the way through 2nd and 3rd gears. It's *definitely* coming from behind me on the passenger side. Once I reach a cruising speed and no longer accelerating, the noise goes away.

As I might have expected, it wasn't there for the drive home. Any ideas?

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My totally uninformed opinion at this point is that it's *got* to be related to the rain I was driving in. Rainy days aren't common this time of year, it might be a while before I can repeat those conditions.

For the record, it was not raining today. So much for that theory. :)
 
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i have a simular noise,,but it happens after car warms up,,i can make it happen when i hold brake down and put load on car keeping it from moving,,try to do this and see if sound comes back,dealer said it was normal,,i dont think so
 
Could it be the infamous crank shaft pulley?
 
After watching the video, my mechanic thinks it's a CV joint.

It still seems to me the noise corresponds more with engine speed than car speed, but he disagrees.
 
After watching the video, my mechanic thinks it's a CV joint.

It still seems to me the noise corresponds more with engine speed than car speed, but he disagrees.

I agree with your mechanic. It does seem to change with wheel speed, not engine speed. It changes with throttle position, but that changes load.
 
As soon as I listened to the audio and before I even read the responses after that post i immediately thought cv joint.
 
Consensus is that it's a CV joint. Oddly enough, it has not reoccured since I added the video in February. I'm not in a big hurry to fix it if it's going to stay quiet.
 
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