hissing from back on acceleration - q45

[totallyjacked]

Is it normal to hear a hissing (almost like someone spraying an aerosol can) coming from the back of the car under fairly hard acceleration? I just bought a 2003 q45 and when I punch the accelerator (doesn't have to be all the way) a hisisng sound like gas escaping or something comes from the back. Starts instantly on pushing the pedal down hard and seems to have nothing to do with speed. I can be going fast or slow and don't hear the noise till I get into the gas pedal hard. Also if I park the car and just mash the engine to rev it - then the noise doesn't happen! Does this sound familiar to anyone?

[konatown]

You need to replace your Fuel Pump and Fuel Pump Control Unit.

Fairly common problem. Could die on you at any moment, spend a couple hundred dollars to buy new and a spend a few hours on a weekend to swap them out.

There's loads of information on this if you use the 'Search' function.

EDIT:

Sorry, wrote that preemptively. I see your other post you list as a 2003 Q45. My advice was for the first generation Q45, but could be something similar.

Also put your information about the vehicle in your profile so it shows under your name, like mine to the left.

[Q45tech]

The new RETURNLESS fuel systems are different frrom 90-96 and 97-01 fuel systems but still the fuel pump increases PSI and rpm with load [throttle position].............a worn or dirty commutator on pump will increase noise.

The usual repair is to replace pump assembly if the noise becomes noticeable.

[totallyjacked]

Thanks guys - I've put 2003 q45 in my profile. So is this likely to be the cause even though I don't get the noise when I mash the pedal and rev the engine up when the car is in park? Also the noise is def. coming from the back of the car - not up front or the engine.

[xerexabante]

i hear a slight whine that comes from brhind the back seat that is where the tank and pump when i accelerate om my car. doesn't bother mo none. i did measure my fuel and its ok. maybe your fuel filter has not been changed.

[totallyjacked]

Hmmm. When I start my q up in initially makes a slight whining almost like it's turboed. This sound seems to come from the engine, is constant (more noticable under acceleration) but then goes away when the car warms up. I wonder if it's related to the hissing from the back under heavy accel... I guess I'll see if I can find a mechanic to check this out and see if it needs a new fuel filter. I can do simple stuff like oil changes but changing a fuel filter sounds way beyond me.

[maxnix]

I believe the fuel filter is in the tank. So no more difficult than cahnging the pump.

F50, Y34 and Y50 owners must learn what G50 and FGY33 owners have, maintenance beyond the factory recommended minimum is necessary for long life of the vehicle without deterioration in performance or expensive component replacement.

[totallyjacked]

Thanks - I've been searching the site and there tons of info on the older q45s but I haven't found how to do this for the 2002+ q's. Is there anywhere on this site with directions for changing the fuel pump and/or fuel filter on a 2003?thanks

[maxnix]

Not yet. The F50 are just now demanding the kind of attention the G50 and FGY33 have for years. Even fuel pump replacement on the FGY33 is not yet documented.

The FSM should be sufficient. Let us know, and if you do it, please document with pictures.

[xerexabante]

i have the same thing its the powersteering pump preasurizing. that is ok. check your fluids.

[totallyjacked]

Well - took it to the infinity dealership and they said the hissing is from a crack in the "y-pipe". Anyway, they want over a grand to fix it so I'll be visiting a muffler shop for a weld-job. Real nice guys at the dealership but my God they charge a lot for a little.

[maxnix]

Dealer will replace it with new (no emissions warranty?).

Shop will weld it.
Modified by maxnix at 3:01 PM 12/30/2007

[qship96]

Are you refering to the Y pipe AFTER the single cat converter that splits to make it appear as a dual exhaust system? If so,it is downstream of converter and not coverede under emmissions warranty.I it is the Y pipe from headers TO single cat converter,it should be covered under emmissions warranty.

[totallyjacked]

The car has 105K miles on it.