The Nissan Path

Hello. After replacing my air filter, plugs, cap and rotor, ignition wires and checking my timing, my pathfinder is still sucking the fuel. I can literally see the fuel needle moving as I drive. I am getting a code for the knock sensor but no other codes. I have an exhaust manifold that leaks slightly but it's not too bad. Any ideas what might be causing such horrific gas milage? There is no fuel smell or leaks that I can find. I'm lucky to get 225km to a tank.

Any help would be much appreciated.

With My '94 3.0, I get approx. 250 miles (U.S.) out of a full tank of fuel.That is with a full tune , new tires at proper inflation,with front end alignment and 2WH conservative driving. I think it's simply the "nature of the beast". Jeep Cherokee's of the same vintage and options are running near the same if they are tended to properly.