[V6-12v] Injector Hiss...

[Elliott Potter]

On Sun, 18 Apr 2004, Nathan White wrote:

> It definitely sounds like its coming from the driver side, non-FPR side,
> from the injector closest to the radiator. I have replaced all vac lines
> except the one coming from the EGR valve, I suppose that could be it,
> but it sounds like its coming more from the front of the engine.
>
> This is very interesting, and I am glad I finally found a lead. It has
> been throwing 02 codes, even with two different sets of brand new OEM
> sensors. Codes have been cleared numerous times with VAG tool.
>
> In addition, there are a few thick rubber hoses around the injectors,
> maybe a hidden leak in one of those?

A leak in one of the large vacuum hoses could make a hissing noise,
sure.  The vacuum booster is connected among the big hoses there.
I had to replace a couple of those hoses in my 90 recently (the one that bends
into the intake manifold, and the next one that hooks into the booster) that
were cracked and that was also making the car run a bit rough.  You
might also try to peer down to where the hose connects to the vacuum
reservoir - it's on the passenger's side, but it's buried a bit so the
sound could travel across.


As far as the O2 sensor goes, always remember to take the
"holistic" view and go for the obvious problems first ... everything
could be related.
--
Elliott


> Thanks for all the help.
>
> Car: 94 100 CSq Auto
>
> Nathan White
>
>
> -----Original Message-----
> From: Elliott Potter [mailto:epotter at eep.burdell.org]
> Sent: April 17, 2004 8:13 PM
> To: Nathan White
> Cc: v6-12v at audifans.com
> Subject: Re: [V6-12v] Injector Hiss...
>
> On Sat, 17 Apr 2004, Nathan White wrote:
>
> > Car has been idling rough lately. Discovered a very noticeable hiss
> > coming from the driver side of the engine. Seems to be coming from one
> > of the injectors. Is the injector likely dead?
> >
> > If I unplug each injector while the engine is running, the sound
> > remains.  Oxygen Sensors (OEM), Fuel filter, spark plugs/wires, timing
> > belt, water pump all replaced.
>
> On automatic transmission cars, there's a little vacuum hose that plugs
> into the top of the intake manifold in the back, right next to the fuel
> pressure regulator - it supplies vacuum to the fp regulator and the
> cluster of solenoid valves by the MAF sensor.  If that hose cracks, it
> makes a very pronounced hissing noise and the resulting vacuum leak can
> make the car run a bit rough (since the vacuum is used by the fp
> regulator).  Could that be the source of the noise?  You don't say which
> injectors the sound seems to be coming from, but since everything in
> that corner of the engine is packed so closely together it's a
> possibility.  Another thing that could make a loud hissing noise and
> cause roughness would be if the gasket between the EGR valve and the
> intake manifold has a crack in it.  That would be on auto or manual
> cars.
> --
> Elliott
>
>
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