I have a 94 V6 Automatic that will only get 10mpg. It was completely rebuilt 1000 miles ago. Since then I have also changed the fuel filter, the O2 sensor, the air filter, cleaned the throttle body, checked timing, and checked for vacuum leaks.

Anything else I should look into?

 

Shouldn't be that low I get about 15 on mine and it has 253k on it and leaks like Exxon Valdez.

3.4 swap

:wabbit2:

 

Heavy check for codes?

I'd guess vacuum leak somewhere those miles of hose.

 

After a complete rebuild you will not get optimum fuel mileage, but after 5-10 Thousand miles you should see a gradual improvement.

 

Check the distributor shaft play, per FSM. Some other dude tried EVERYTHING... still getting 10mpg. If the distributor is out of spec the ignition advance won't be accurate, leading to knock and retardation.

Just a heads up, the dude mentioned checked about 4 different distributors (2 rebuilt, 2 junkyard)... found all to be out of factory spec. Can't remember which brand #5 was, that was actually in spec. Solved his issue finally.

Also maybe check knock sensor, and wire to and from the sensor.