Severe gas milage decrease

My 98 Trooper used to get 22 mpg (regularly checked). Since moving to California my milage has decreased to 10 to 11 mpg! I've checked everything, replaced plugs, o2 sensors and air filter, even took it to the dealers shop (couldn't find any problem). I am extremely frustrated. This has been a great vehicle but I can't afford 10 mpg at $1.75 for a gallon of gasoline. I haven't replaced the fuel filter yet as I can't find it (if anyone could tell me where it's located I would appreciate it). Has anyone else out there experienced such a drastic change in milage? If so, do you have any reasons and, most importantly, corrections>

Thanks

I am also realizing crappy 10-13mpg here in L.A. This was a used car purchase so I didn't bother to check what's the original mpg suppose to be like. I was shocked to find ~20mpg to be the norm. What's going on? i'm hoping someone here can shed some light on this nasty mpg. At this rate I should be driving a Hemi instead!

My 98 Trooper used to get 22 mpg (regularly checked). Since moving to California my milage has decreased to 10 to 11 mpg! I've checked everything, replaced plugs, o2 sensors and air filter, even took it to the dealers shop (couldn't find any problem). I am extremely frustrated. This has been a great vehicle but I can't afford 10 mpg at $1.75 for a gallon of gasoline. I haven't replaced the fuel filter yet as I can't find it (if anyone could tell me where it's located I would appreciate it). Has anyone else out there experienced such a drastic change in milage? If so, do you have any reasons and, most importantly, corrections>

Thanks

I'm just a shade tree mechanic, but here's where I'd look. If the engine is running normally, has power and isn't misfiring under load, then it must be firing on all cylinders with correct dwell/timing. If not, your gas mileage will be terrible. Please don't be offended, but are you sure the transmission is shifting into overdrive? You probably checked the RPM for that. You could have a frozen caliper and be dragging a rear brake. A front one would be more noticeable pulling to one side. This knocked down my mileage by about 5 mpg one time. Next time you return from a ride, see if one of the wheels is HOT. Another thing I'd check is fuel quality, esp no water in the system. Not sure if it freezes where you live, but icing screws up carburetion (using dramatically more fuel to air), not sure how/if it affects the Trooper's injection system. Have you ever had your injectors cleaned? Cheapest way is to put BG44K in a tankful of gas. This product works! Good luck with those CA fuel prices!

22MPG? Yours is probably the only 3.5l Trooper ever made to get that kind of mileage :). Typical is closer to 16MPG.

I'm replacing the Timing belt on my 98 trooper 3.5L Can anyone tell me how to set the timing mark?

Any help would be appreciated.

You guys think that's bad. I get about 10mpg and gas here in Belize is at about $4 USD.

I can't figure out a good cause and or explanation to the fuel eating demons either. That's why I bought a Civic! Now my Trooper just looks good in my garage. I tow my motorcycles around, that's about it. Now that I can tear into it though, I'm planning a manhunt for those demons!