Sounds just like my ex's '93 Altima from what I can hear in the recording -
no powertrain problems through it's 153K-mile lifetime until it got smooshed
by an Infinity SUV. Concerning the other noise, I have known 2.4L Nissan's
to be picky about oil filters. Some non-Nissan oil filters lack an effective
anti-drainback valve which can cause some noise for a few seconds on
startup.

Roger

"JM" > wrote in message
...
> I've got a 99 Nissan Altima with an odd sound to it while accelerating.
> It's a
> regular thrumming, sort of "fluttery" sound. My 94 has a very similar
> sound
> as well, but a bit more harsh I think (due to less sound deadening maybe),
> so it could very well be normal. I'd really like to know what causes it
> though.
>
> I went for a drive and recorded the sound inside the cabin, it's a bit
> hard
> to make out but any time I accelerate it's there. It's most noticeable
> under moderate acceleration it seems.
>
> I've got a short clip and the full length at
> http://www3.ns.sympatico.ca/pmason/altmp3/.
>
> To me it almost sounds like a resonance that is happening somewhere, in
> the
> exhaust manifold maybe or some part of the engine bay. I had a Civic a
> few
> years ago that due to an accident and repair had the engine mount touching
> the frame of the car and unless I wedged something between the two parts,
> I
> would get nasty sounding knocking/vibration while driving. Maybe this is
> the same sort of thing. It's almost like some metal part of the engine is
> vibrating against the hood, or the frame, or something.
>
> Also, I get a slight tapping for 1 or 2 seconds at startup when the engine
> is warm (but has been sitting for maybe 20 minutes). You can make it out
> faintly at the start of the longer recording here. I've been told it may
> be
> a stuck lifter, so is there any chance that that could account for the
> noise? It seems to happen at about the same frequency or tempo as this
> sound, taking the lower idle rpms into account. I would expect something
> like that to have a lighter sound to it
> than this does, but I'm no expert. I've been telling myself that it's
> happening (revolving) too quickly to be something to do with a particular
> cylinder or valve, but again, I'm just guessing.
>
> I know it's pretty hard to make any guesses, educated or otherwise just
> based on a couple of hard to make out samples, but I would like to hear
> any
> theories just the same.
>
> Thanks!
>
>
>
>
>