[V6-12v] Injector Hiss...

[Elliott Potter]

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