1stDeuce
Explorer
Jeff, did you ever get this resolved? As an earlier post said, the upstream sensors are for air fuel ratio, the downstream sensors just monitor cat performance... poorly. Other than to get a CEL light to go off for a bad downstream sensor, I don't ever replace them since they have no effect on mileage.
You've put a lot of miles on it since buying it, and I'm sure even more over the last year... Hopefully you figured it out, but if not, here's my list of things to check:
Dragging brakes (are any of them hotter than the rest if you drive for a while and then stop?)
If you have an engine driven cooling fan, check to make sure the fan clutch isn't stuck engaged.
Tire pressure?
Tire design different? (Mud tires will drop the mileage by as much as 2mpg, especially on smaller rigs.
Bunch of crap bolted to the roof? Even an empty expedition rack will take mileage off on the hwy. Less effect in the city though...
Auto vs. manual?
If the cats are plugging off, it may use more fuel, and you might not get the foul smell unless you drive with the rear window open. Aftermarket cats will work just as well as factory. I'm running a glasspack "resonator" in place of the cat on my Jeep, and it doesn't throw a CEL ever. And I got a "fast pass" both times I did the CO emissions test.
Seafoam or STP injector cleaner every once in a while shouldn't hurt.
How about checking fuel pressure? If it's low, you'll get a horrible spray pattern, and worse mileage.
Timing? My Jeep is a dog compared to others. I'm sure it's because the base timing is retarded because of a badly machined flywheel, or the cam is running one link off. Just haven't taken it apart yet. If someone messed up the cam timing by one tooth, it might make it doggy w/o causing interference. Production engines are not always assembled perfectly... You may have gotten a Friday or Monday engine like mine.
Ok, back to work...
Chris
You've put a lot of miles on it since buying it, and I'm sure even more over the last year... Hopefully you figured it out, but if not, here's my list of things to check:
Dragging brakes (are any of them hotter than the rest if you drive for a while and then stop?)
If you have an engine driven cooling fan, check to make sure the fan clutch isn't stuck engaged.
Tire pressure?
Tire design different? (Mud tires will drop the mileage by as much as 2mpg, especially on smaller rigs.
Bunch of crap bolted to the roof? Even an empty expedition rack will take mileage off on the hwy. Less effect in the city though...
Auto vs. manual?
If the cats are plugging off, it may use more fuel, and you might not get the foul smell unless you drive with the rear window open. Aftermarket cats will work just as well as factory. I'm running a glasspack "resonator" in place of the cat on my Jeep, and it doesn't throw a CEL ever. And I got a "fast pass" both times I did the CO emissions test.
Seafoam or STP injector cleaner every once in a while shouldn't hurt.
How about checking fuel pressure? If it's low, you'll get a horrible spray pattern, and worse mileage.
Timing? My Jeep is a dog compared to others. I'm sure it's because the base timing is retarded because of a badly machined flywheel, or the cam is running one link off. Just haven't taken it apart yet. If someone messed up the cam timing by one tooth, it might make it doggy w/o causing interference. Production engines are not always assembled perfectly... You may have gotten a Friday or Monday engine like mine.
Ok, back to work...
Chris