Oxygen sensor can hurt fuel economy
Q: Our 1999 Mercury Cougar two-door hatchback has been regularly service from the outset and is in good running condition.
But I've noticed a considerable drop in fuel economy in city driving.
Our highway gas consumption hasn't changed much.
What might account for this?
A: Technician Tony Prochilo replies:
Fuel consumption will vary based on vehicle speed, outside temperature, weather and traffic conditions, tire pressures and regular engine maintenance.
That last one includes tune-ups and using a good quality, energy-conserving motor oil.
As well, your Mercury's accessories (particularly a/c) will also affect your fuel use.
Another important but often-forgotten factor is a car's oxygen sensor. Mounted in the exhaust system, this device monitors the oxygen content of the exhaust gases.
The on-board computer uses this information to maintain a proper air/fuel mixture during vehicle operation. This will ensure maximum performance, economy and driveability while controlling vehicle emissions.
If the Cougar's oxygen sensor has not been replaced recently, have a repair facility check it out. A lazy sensor can provide inaccurate information for fuel delivery.
On an older vehicle, a slow-performing sensor may not illuminate any warning lights, but can cause the fuel concern you cite.
Q: I have a front-wheel-drive, 2005 Pontiac Montana, with a 3.5 L V6 (43,000 km) and four-speed automatic. The van has self-levelling air lift in the rear.
If I haul a 1,225 kg, 4.8 m camper trailer, can I use an equalizer hitch or would this throw out the Montana's computer when it tells the air ride when to come on.
RV dealers say you should not use an equalizer hitch with air assist.
A: Technician Peter Lokun replies:
Hopefully your van is equipped with a trailer tow package.
Besides the obvious accessories such as a trailer hitch and a trailer wiring connector, this package includes heavier suspension, an upgraded transmission and a required transmission cooler.
Without it, the trailer you're towing will most likely shorten the life of the Montana's major components, such as your transmission.
The Level Ride system is designed to automatically maintain the proper rear suspension ride height when weight is added to or removed from the vehicle. An equalizer hitch accomplishes the same objective as Level Ride, so avoid using such a hitch.
If your van is not equipped with a heavy-duty suspension or a trailer tow package, you may damage or prematurely wear out the air lift shock absorbers or Level Ride components. The trailer you're towing is at the limit of a standard suspension's capacity.
Although air lift shocks support added weight on a cushion of air, the springs are still the major weight carrier.
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