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Be sure to replace the O2 sensor. That's a big one especially if it's high miles and has never been changed. Answer Things to check/try in order to improve fuel mileage on almost any vehicle: 1) Tire Pressures. Are tire pressures no lower than manufacturer recommendation? Remember to check tire pressure in the morning (when cold), and that a 10 degree (Fahrenheit) drop in outside air temperature will decrease tire pressure by about 1 psi. Also, some tires, especially older ones, may "leak" up to 1 psi per month. If pressures are too low, try to visit a station near home, and put in 3 or 4 more psi than you want - after a few hours or next morning, check pressures and bleed any extra pressure. Why: tires may read 3 or 4 psi higher after a few miles' use vs when cold. 2) Alignment. May need alignment. Can't really tell without putting it on an alignment rack, unless it's pretty bad, in which case you may see uneven wear (especially on front tires). 3) Brakes. One or more brakes may be sticking (especially front). I've had this happen on BOTH our vehicles. 4) Bearings. One or more wheel bearings may be binding/failing (unlikely, but possible). 5) Oil. Are you using 5W30 oil in cold weather and 5W30 or 10W30 in hot weather? Changing oil AND FILTER regularly (at least as often as manual says)? 5) Vacuum hoses. Check that all vacuum hoses are secured and intact. 6) PCV. Replace PCV valve (as you face engine from front, it's way in the back left corner, almost as far as you can reach; narrow space so it's a bit tedious to change, but no tools required - about $5). 7) Wires. Are ignition wires in good shape (ie, no cracks, etc.)? 8) Other. One or more engine accessories (alternator, Power Steering pump, air conditioner, water pump, etc.) may be binding (unlikely but possible). 9) Heating and Air conditioning will have a lot on fuel consumption in addition to driving habits, city driving or highway driving. A big difference in fuel consumption when driving 60mph (~100kmph) and 80mph (~130kmph) on highways. Answer i would strongly suggest replacing the mass airflow sensor in this case. when they get dirty, the computer cant tell how much air is going into the intake, thus to the combustion chambers. so when it gets to the exhaust, the air fuel ratio sensors see alot of air. when these sensors see a lot of air (02), the computer holds the injectors open longer to compensate. this extra fuel adds up to loss of mpg!

      • WAIT! Before you replace that horribly expensive Mass Airflow Sensor, pull it out and *carefully* spray it clean with brake cleaner or an electronic cleaner of some sort. And do NOT touch any of the itty-bitty wires inside with anything or you WILL be replacing it. Anyway, an awesome Toyota mechanic told me to do this before replacing it and it improved performance tremendously! He said the sensors were notorious for getting all gooped up and sure enough, he was dead-on right. After 112,000 miles, ours was covered with gunk. I should have cleaned them at 75,000! Our 2000 Sienna can spin the tires at a stop light again. Also, installing a K&N type oiled filter can also contribute to the build up so be aware if you do that too.
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โˆ™ 2016-01-21 16:13:23
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Q: What to do to increase 2001 Sienna fuel mileage to original 21-23 mpg from current 18 mpg if new plugs and air filter haven't solve problem?
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