JM wrote:
> JM wrote:
> > Comboverfish wrote:
> >>> Forgot to mention, no codes set, and I cleaned the EGR and ports when I
> >>> got the car (had the problem then also). Also, if I pull the vacuum
> >>> line to the EGR valve, effectively disabling it, there's no change. It
> >>> does feel like that kind of a problem though
> >> If I had it I would look at fuel trim with a scantool, under many
> >> different driving conditions. If fuel trim was too far off I would
> >> suspect dirty MAF sensor elements first. I suppose that you have
> >> checked the integrity of the large intake hose (splits, cracks, fit)?
> > Yes, I've been over that hose and the various ones that branch off of it
> > a few times, and everything seems in order. I don't have a tool that
> > will let me see the trim values but I'll keep that in mind in case I do
> > take it somewhere for another look.
>
> I was out today and noticed there is a distinct hissing sound when I rev
> the engine coming from somewhere around the EGR valve or possibly the
> intake manifold. I know this particular year Altima was known for the
> intake manifold gasket breaking down and leaking, but this sounds like
> it's closer to the firewall than that.
>
> I went over all the vacuum lines I could see and they all look good, so
> I'm a little puzzled where this sound is coming from. I have tried
> shooting throttle body cleaner where the manifold bolts to the head,
> with no change in idle, and I also sprayed around the various metal bits
> of vacuum line, but this had no effect.
>
> I'm half hoping I'm on to something though...

You may just be paying more attention to the sound of the idle speed
control than normal. As it opens up (revving the engine up and down
will cause this) more air will rush through the intake tube and cause a
sound like you describe. Unplug the ISC connector and try again. See
if this is the noise you are chasing.

Toyota MDT in MO