Gas mileage

[crankcase1943]

Hey friends, I got a 95 Grand Caravan with 3.3 engine. Gas mileage is low I think. 13 around town, 20 on the road. The last time I went on the road about 3 weeks ago the check engine light came on about 40 miles up the road. I pulled the code. It is a code 51. Code 51 indicates the O2 sensor is stuck on lean. Does this mean that it is telling the ECM that the mixture is lean all the time and needs more fuel? Also when I start going up a long hill the AC will stop blowing out of the dash and start blowing out of the defroster and heater ducts. I have checked all the vacuum lines I can find under the hood. All seem to be attached and tight fitting. Any help on both of the question would be a lot of help.

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[next2pool]

Fuel economy is a tough thing to compare between cars and drivers, but it does sound low. It should be closer to 18 city and 26 highway--give or take a few. A bad O2 sensor definitely can cause this. As far as your HVAC issue, it indicates low vacuum which does occur during wide throttle opening. I'm not sure if the 95's had a vacuum reserve tank or a check valve--you may want to trace some of the hoses directly from one end to another. I don't have a manual for that generation. The ssytem goes to "default" position when there is low or no vacuum. The later models went to electrically driven mode door actuators.