So, my 05 ZX4 Focus has really bad gas mileage, at about 18MPG. The body of this car has 205k on it. I don't know what the engine has on it, previous owner didnt tell me, but judging by how clean the inside of the engine is I would say it definitely isn't 200k.

The car runs amazing, starts right up, no drivability problems at all. Only thing is high idle at startup, but then it corrects itself. Since I've had the car, I've done new spark plugs, a new fuel filter, a new air filter, the belt, O2 sensors, a couple of oil changes, the works. I am looking to get the gas mileage back up to where it should be. BTW, it is throwing absolutely no codes at me. It does run rich, but not enough to trigger any codes. Can anyone point me in the right direction as to what to do?

 

Have you cleaned the mass air flow and intake temp sensors? If they're dirty, they can be providing false readings to the CUP causing it to run rich with the O2 sensors doing their best to help correct what they can.

 

Does the coolant temperature sensor seem to work OK ? If they are bad , it will give false information to the " computer " and the " computer " will run the mixture rich .

Also check for loose electrical connections and vacuum hoses .

God bless
Wyr