Possible Fuel Leak?

[Jezza_hr]

Recently my fuel consumption has been getting worse and my revs getting less (despite asjusting the idle speed). I now find that £30 of petrol only gets me 100 miles on the clock (from full tank to quarter) Now looking at my mileage today I may just only get 70 odd miles from a full tank

I'm going to get under the car on sunday and check it out. Does anyone have ideas where I should be checking for leaks? or if anything else could be causing it?

[banpei]

Are you sure your right foot didn't became heavier over night?
Seriously: all I can think of is your butterflies or vacum not working correctly...

[Yonzie]

Get one of those Weed-burners for the garden.
Use it on the weeds under the car. Then you'll find that leak pretty fast.

You may want to have someone standing by with a CO2 type fire extinguisher ;-)

[Matt Skinner]

A fuel leak wouldnt effect idle speed as the fuel pressure regulator will just increase pressure to compensate

A vac leak, would show up as an icrease in revs at idle so wont be that.

Likewise worn butterfly spindle, that tends to increase idle speed.

I'd suggest a compression test or better yet leakdown test. If your valves have stopped sealing correctly its gonna be pumping unburned fuel down the exhaust rather than igniting it. Another indicator of this would be a smell of fuel from the exhaust. An exhaust gas analyser would also show very high hydrocarbons if this is the case.

[Ivan141]

What type of management does your car have? MAP or AFM? The AFM versions have an 02 sensor that might cause problems, so if you have one it's a possibility. AFM's can also go bad, but that's pretty rare.
If your engine lacks power then you most likely have some problems under the bonnet. Real fuel leaks tend to have a prominent smell..
Check under the car for wet spots/petrol smell, if you find none then do a readout of the diagnosis system. You never know, an error code might point you in the right direction (although it often spits out the TPS error code when something else is wrong).
Is your watertemp sensor connected and working properly?