Strange noise!!

OK, I have been beating my brain out this week trying to figure out what the heck is going on, and I have decided to let you all help me out. I have this strange noise when idling that quickly goes away upon acceleration, however it is still in the background as the engine RPM increases. At idle, I'd swear that there is a rock rolling around in the engine, it sounds like a bearing knock. The problem is that the engine is running perfect, well as perfect as you can get for 250K miles on it. I have removed the serpentine belt to see if it has anything to do with any of the accesories, no difference. No stalling, check engine lite is on, (but then it's been on for the last 40 or 50 K), this is almost certainly some kind of "sheet metal" sound, if you know what I mean. I have been all over the engine and cannot find anything obviously wrong with it, nothing externally apparent at all. I have used a mechanic stethascope, and I don't think that the noise is actually internal, as I cannot hear it inside the engine, just the normal sounds of the driveline. I have jacked it up while running to see if it might have to do with the motor mounts, but that doesn't seem to make a difference. Car runs as good as always, and the noise seems to be most noticable from underneath, towards the driver side if that helps. I drive this puppy 100 miles a day, and the noise has gotten a little louder, but basically stays the same, it is really noticable from about 600 RPM up to about 1500 RPM, then it just fades away only to return after you come to a stop. At idle in D it is quite noticable, if you flip it into neutral, it goes away. Anyone have any great ideas? I'm all ears!!!:banghead::banghead:

try some higher octane fuel, maybe a bit heavier of an oil (10w30 instead of 5w30 in the summer weather)...and get it code scanned to see why that engine light is on. When you throw it in gear there is more idle load on the engine, so it would make sence that it goes away in neutral.

First please let us know if you have the 3.5L engine or the 3.8L

Sorry, forgot to mention that it is a 3.8. It is not an engine knock, I have already tried the higher octane route and the heavier oil route, no difference. It actually sounds like there is something hitting a rotating part of the engine on occasion, that is what I meant by the sheetmetal noise. I have poked around until I am dizzy and I cannot find anything that is obviously hitting externally that would be visible like a shiny tooth on the flywheel, etc. Code scans have revealed a multitude of sensor issues, but I am way to cheap to replace all of the issues that show... it has had no problems for the last 40~50K miles, do you suppose this might have something to do with the EGR? (just guessing at this point) I am certain that this is a simple mechanical issue, not related to electronics. like I said above, I'd swear that at idle there were a few rocks rolling around inside the engine, but it has been making this noise for about a month now.... I should also let you know that I have just recently become employed again after being laid off, so money is pretty tight right at the moment... Another clue is that neither oil pressure or consumption are an issue.

:2cents: Is the exhaust system vibrating on the hangers?

A failing harmonic balancer is one possible cause of this type of noise,no one online can accurately diagnose this type of noise without hearing it. Oilweight and octane almost never cure any type of engine noise other than to act as a " masking agent" Take the belt off see if there is any change in the noise.

I have removed the serpentine belt to see if it has anything to do with any of the accesories, no difference. No stalling, check engine lite is on, (but then it's been on for the last 40 or 50 K), this is almost certainly some kind of "sheet metal" sound, if you know what I mean. I have been all over the engine and cannot find anything obviously wrong with it, nothing externally apparent at all. I have used a mechanic stethascope, and I don't think that the noise is actually internal, as I cannot hear it inside the engine, just the normal sounds of the driveline. I have jacked it up while running to see if it might have to do with the motor mounts, but that doesn't seem to make a difference. Car runs as good as always, and the noise seems to be most noticable from underneath, towards the driver side if that helps. I drive this puppy 100 miles a day, and the noise has gotten a little louder, but basically stays the same, it is really noticable from about 600 RPM up to about 1500 RPM, then it just fades away only to return after you come to a stop. At idle in D it is quite noticable, if you flip it into neutral, it goes away. Anyone have any great ideas? I'm all ears!!!:banghead::banghead:

I have heard of someone having a torque converter bolt come loose, have you had any trans work done at all? Does it do it when in Park? What ever it is, sounds like it is related to torque happening when in gear. Maybe your dog bone is bad, being the bushings inside it. I guess I am not sure if the 3.8 has that or not. I would assume that it would, my Mom's Buick LeSabre (http://en.wikipedia.org/wiki/Buick_LeSabre)has one.

I thought about the harmonic balancer, replaced that about 12K miles ago. Sounds just like it did then, as a matter of fact. Took the belt off last weekend, no change in sound, so that kind of rules out all ancillary attachments... I have yet to look closely at the exhaust, will do that this weekend, could be the motor mounts I suppose... I realize it is almost impossible to diagnose over the net, just looking for possibilities, please keep 'em coming. I'll let you know what I find out. Torque converter bolt is a possibility, I had the tranny replaced about 45K ago. I'm fairly convinced that it is something loose, WHAT is the question!

Mark

I thought about the harmonic balancer, replaced that about 12K miles ago. Sounds just like it did then, as a matter of fact. Took the belt off last weekend, no change in sound, so that kind of rules out all ancillary attachments... I have yet to look closely at the exhaust, will do that this weekend, could be the motor mounts I suppose... I realize it is almost impossible to diagnose over the net, just looking for possibilities, please keep 'em coming. I'll let you know what I find out. Torque converter bolt is a possibility, I had the tranny replaced about 45K ago. I'm fairly convinced that it is something loose, WHAT is the question!

Mark

How common is the harmonic balancer problem?? Don't mean to hijack your post. That is just not something I have heard of before on this page, or otherwise.

Harmonic balancer is comprised of two pieces of metal bonded together with a rubber insulator in between the two metal pieces. What happens is that the rubber deteriorates and the two pieces of metal start to work apart. By the time I replaced mine, the pulley had chewed up the serpentine belt to about a third of its original thickness. I was lucky, it would have made a big "BANG" when it finally let go!

Been a while so I thought that I would update... It appears that the issue is directly related to the motor mounts. Even the starter is acting funny now, and that's after I put a remanufactured one on over the weekend. Now to find someone to replace the motor mount for me...:popcorn:

Been a while so I thought that I would update... It appears that the issue is directly related to the motor mounts. Even the starter is acting funny now, and that's after I put a remanufactured one on over the weekend. Now to find someone to replace the motor mount for me...:popcorn:

Have you checked for a cracked flexplate? This can cause the rocks in the engine noise you are describing and if it gets bad enough could cause starter engagement problems as well. Good luck!

Turns out it is the flywheel! I'm going to have my mechanic replace it as well as put a new oil pan gasket and motor mount.. he quoted me $585 for everything, I think that I will have him do it as I haven't anyplace to drop the tranny etc.:runaround:

Turns out it is the flywheel! I'm going to have my mechanic replace it as well as put a new oil pan gasket and motor mount.. he quoted me $585 for everything, I think that I will have him do it as I haven't anyplace to drop the tranny etc.:runaround:

Glad to hear you found the problem! Sounds like a pretty good deal for all the work involved.

have your tech replace the rear plate seal while the drive plate is being replaced, they have a tendency to leak, as well.

Well, it always happens to me! New flywheel, motor mounts, put it back together and the trans output shaft is shot, bearing toast, and the engine vibrates like crazy! Now gonna' have to put in another tranny, found one for $500, other than that, all ok now. Just hope the landlord doesn't evict me now 'til I get caught up on that!