Under The Hood: Low mileage puzzles Escape driver
Published: Friday, June 22, 2012
Updated: Friday, June 22, 2012 11:06
QUESTION: I have 2007 Ford Escape with 90,000 miles. I have been noticing I am getting very poor mileage per gallon and air conditioning is also very poor. I have asked my trusted mechanic, and he does not have any good suggestions. Can you please suggest what could be causing this?
ANSWER: Gas mileage has to be one of the most difficult topics to get a handle on, as there are so many variables. Depending on the Escape's engine _ 3.0 liter V-6 or 2.3 liter four-cylinder _ transmission type, and trim level, the EPA's fuel economy ratings range from 17 city, 21 highway to 21 city, 27 highway miles per gallon. And everyone knows these are tough to match, especially the city number.
An even weightier variable is how the vehicle is driven. Cold weather, frequent cold starts and short trips, and stop and go traffic could easily cut the city number in half.
Driving techniques are also a big factor, as well as tire choice, proper tire inflation and minimizing unneeded cargo. Each time the brakes are applied, hard-earned kinetic energy is burned off as heat.Coasting, rather than braking, into traffic slowdowns can make a noticeable difference in fuel economy. With the manual transmission, lugging the engine slightly rather than allowing it to rev improves efficiency; the further open the throttle is, the less pumping losses occur. Tall, thin, hard tires roll more easily than wide, sticky performance-oriented tires, and running them at or slightly above the door sticker number provides the best fuel performance.
You didn't mention if the fuel economy had recently dropped or has been continually disappointing. With the Escape's engine diagnostics, it's unlikely a significant problem could be occurring that would affect fuel economy yet not illuminate the check engine light. There are certainly things that can go wrong with an engine, such as valve or cylinder sealing problems, air-fuel ratio or ignition timing faults, an exhaust restriction, or even transmission issues that result in incorrect shifting or an inoperative torque converter clutch. In just about every case, the sensors or actuators involved, or the inferred readings they provide, would indicate a fault that raises emissions or cuts into engine efficiency, and result in a glowing indicator.
Could your mileage have dropped due to the installation of a new set of tires or a change in driving routines? Your technician has surely checked the air filter, scanned for codes and the like.
Poor air conditioning performance could be due to insufficient refrigeration or improper blending or delivery. I'll assume the discharge air exits the correct registers at the proper volume and simply isn't cold enough. A check of evaporator temperature and system pressures would verify proper compressor function, orifice tube operation and pressure cycling switch values. Proper cooling of the condenser in front of the radiator is really important _ it must be free of debris and enjoy proper fan operation. Your Escape uses an old-school cable-operated temperature blend door. A check might be made to ensure it is properly adjusted, so heat isn't accidentally blended in with your cold air. The recirculation door can also be checked for proper function; it's used during Max A/C mode to recycle already-cooled inside air, rather than bringing in hot outside air.
ABOUT THE WRITER
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at email@example.com; he cannot make personal replies.