Gas mileage getting worse...
 

I was driving my RX with no trailing ignition, and my fuel milage was hurtin because of it. I fixed the problem, and advanced my timing a little. Now I'm lucky if a quarter tank will get me across town. I'm guessing I'm getting about 250km/tank in the city. Anything that could be causing this?

The car is bone stock except for a stright pipe exhaust. No cats, no resonator, just a straight trough muffler.

Did you replace your trailing plugs? They would likely have fouled.

Hopefully it isn't a fuel leak? Does your gas cap seal tight? Any signs of leakage around the filler? Can you smell gas when you run the car? If so, do you see any drips?

I had the car up on a hoist today, and no leaks what-so-ever. I havent changed the plugs yet, but you think that a fouled plug would be worse than a non-firing plug all together?

Start with a full tune up, plugs, cap, rotor, air/fuel filter and plug wires if they are more than a few years old. Run a can of Seafoam through the fuel tank. Are you having any driveability issues? How far did you advance the timing?

You might want to check the brakes too, in case you have a dragging caliper or the e-brake cables are hanging up.

check the VALVES and PISTON RODS =D

some one had to say it.

Brakes are fine, i dont have any major driveabilty issues other than a little bit of chokeing on hard launches, but its only in third. Basicly when i hit 5000rpm in 3rd at wot it chokes up for a second... It feels to me like the clutch is slipping, but its only got 20k (KM) on it.

i think u blew the headgasket...LOL

I actually had a co-worker try to find a PCV valve on my car (work at mr.lube)... he looked for a good 5 minutes while i was laughing.