zer0c123

1993 240sx Manual Base model 161k miles. No engine mods besides bolt-on AEM intake.

I've always had some suspicion an exhaust leak before the CAT was the cause for a loud growl noise and vibration that I can hear in the cabin. The majority of the time, this noise and vibration occurs when accelerating at 60-75 mph. Lately it has been much more consistant at that speed range. The noise sounds as if I had shifted into a higher gear at low rpm; therefore, kind of loud growl noise. Another to think of it is if you drive on those rumble strips that placed on the shoulders of some highways. Or you could say it sounds like a truck. I can’t pinpoint the location of the noise, but it seems like its everywhere in the cabin. Same thing with the vibration, I can feel it in the steering wheel and in my seat. If I let off the gas, the noise and vibration goes away, but returns if I get back on the gas whether full throttle or partial. I usually have to accelerate to over 75 mpg for the noise and vibration to go away.

Also last month, I ran seafoam and saw a little smoke from the flange where the exhaust manifold bolts to the exhaust piping ( right after the O2 sensor). It was hard to tell, because looking from the top at the EGR pipe threaded into the manifold is . Therefore the smoke could be from the flange or the egr pipe at the exhaust manifold.

Well,I just got back from a muffler shop, where the tech used a stethoscope around my exhaust system and manifold, but he could not hear any exhaust leak. Also, he saw no black soot to indicate an exhaust leak.

I don't think it's by wheels, because the nose goes away if I let off the gas. Also I recently had all 4 tires replaced with an alignment.

Now i'm at a loss on what is causing this noise. Anyone have an idea?

ka4life87

First u gotta figure out if the noise is coming from the engine or drivetrain, when you hear the noise throw it in neutral, if noise goes away possibly its ur engine, if it doesnt then drivetrain could be ur center carrier bearing for the driveshaft or hub hearings are going out, many possibilities