[boonah2000]

Can somebody help? I'd like to start this by saying that I know that the problem I am going to describe has nothing to do with the air intake scoop.

After getting off the interstate in my 2003 SL (15K miles) a month ago I came to a stop at a red light. When I accelerated at green, I heard a grinding/rattling noise (almost a plastic type of sound more than a metallic grinding). It happened at low speed and went away. Since then, I noticed that it happens a lot when turning and accelerating. At first it sounded like it was coming from the right side of the car, under the passenger's feet. Now it sounds like it is coming from under the car/engine, not necessarly to the right.

Well, since then (and I don't know if they are related), I experience a noise when accelerating and it is different than what I describe above. When accelerating from a stop or low speeds, there is a sound that sounds like a smaller engine accelerating. It goes away after I get past the lower speeds. If I stop and rev the engine, I can hear what I can only describe as a noise similar to that made when an exhaust pipe has a small hole in the muffler.

What makes this worse, is that it is not consistent. However, it does happen daily. The Nissan dealer has heard both noises that I describe and has done nothing to fix them. Their best advise is that it is the gas. I know what bad gas sounds like and this is not it.

I am getting very frustrated with a car I like very much. I'm hoping someone here can give me some advise that I can take to the dealer (preferably the solution).

 

[GripperDon]

Possibilities Thoughts that might help you track it down.

Sounds like it happens only when you are doing things that can "Rock the engine" by asking for a large change in torque. Therefor may be their is something that occurs when the engine reacts to this torque by rotating.

This might be an engine mount or something that rubs the engine only when it has "Moved"

A pulley, a piece of sheet metal or heat shield rubs against the engine, etc.

You can try a different dealer.

Just some thoughts, maybe they will help. Best wishes, be patient it's a unique vehicle and not perfect but good.

 

[boonah2000]

Their response yesterday was to adjust a heat shield. Didn't fix anything.

The mechanic heard the "hole in the muffler" sound yesterday. This is the one that has me most concerned. I am convinced that this is also what is causing the "small engine" sound I describe. I'm not sure what adjusting a heat shield is going to do for this. There is another dealer roughly 30 miles from me, but I am afraid that I am going to get similar responses.

 

[GripperDon]

Well he seems to have checked out the Engine Torquing" possibility. Maybe there is a loose set of bolts on the flange of some joint in the exhaust system that requires the parts to be hot and therefor bolts to microscopy lengthen and a gasket start to let some exhaust gas escape and make the sound. Maybe you can ask the dealer to check or tighten up all the bolts on the flanges etc. of the exhaust system.

 

[boonah2000]

GripperDon, I too am a graduate of the Univeristy Of Florida! I just read your page. I am a Gator living in Tallahassee of all places.

 

[GripperDon]

GO GATORS! Class of 58!

 

[Eric L.]

Why wouldn't it be a hole in the exhaust pipe. I would check the "front exhaust pipe" under the engine, maybe you hit something on the road and its bent or punctured. I had this happen on my 97 Maxima, and it made a terrible squeaking sound that took me six months to diagnose.

Other thoughts are transfer case gear noise. Maybe have the dealer check the fluid level.

 

[GripperDon]

You may be right!. I had discounted the constant hole beacuse "It goes away after I get past the lower speeds. So this put me on the engine torque induced situation which includes the exhaust system.

 

[boonah2000]

I'd like to think the dealer would notice a hole in the exhaust, but I can't be certain. If the hole is small enough, once enough exhaust builds up, the noise will lessen (at least that was my experience on another car I had many moons ago).
I have a feeling I'm in for the long haul in diagnosing the problem. I have another appointment with the service manager tomorrow. I am afraid that he will be the third person that has heard the problems only to tell me to try new gas.

 

[Eric L.]

Check for a hole in the flexpipe section of your main exhaust pipe. I've heard of a "bees in the can" noise from defective flex sections on other Nissans, which can come and go at different speeds.

The hole might not be visible because the flex section might stretch and open up a small hole under hard acceleration.

 

[boonah2000]

Thanks for the advise. If I mention the "flexpipe section of the main exhaust" are they going to know what I am talking about?
For my own education, how would you describe the section. The sound seems to come from right under the gear shifter. If you opent the driver door and rev it, you can hear the "hole" sound.
Is this the error you are referring to?

 

[Eric L.]

Yes the dealer will know what the flexpipe is. You can look at it yourself - it looks like a metal mesh and its part of the exhaust pipe.

Under your shifter eh? Thats where there is a large resonator. It looks like a cat, but the FSM clearly says its part of the exhaust pipe and not a cat. Maybe there is a clog in there? Who knows. Worth another check.

The dealer should use chassis ears (a stethescope thing) to diagnose this problem if it isn't obvious where the noise is coming from.