Automania/Repair & Maintenance

AUTO QUESTIONS AND ANSWERS FOR WEEK 46

by Bob Hagin

Q. I recently bought a new Toyota Tacoma. It has the four-cylinder engine and an automatic transmission. The instruction booklet that came with the truck suggests that I drive it the overdrive position all the time to increase mileage and save fuel. However, a few years ago I read one of your articles in which you recommended the use of overdrive only on the freeway or for highway driving. Do you believe that they have improved overdrives or do you still recommended its limited use? R.C. Elk Grove, CA

A. Vehicle makers want their buyers to drive in as low an RPM range as possible for many reasons not the least of which is that driving in that manner increases the fuel mileage a bit. When the manufacturers submit their documentation on new cars and trucks, this increases their corporate average fuel economy which means that they can build more high-end cars which traditionally get those low MPG numbers. You might remember that back then some stick-shift cars had small lights on the dashboard that were operated by vacuum switches. When the engine vacuum value went low, the light came on and the driver was supposed to shift up. No one did, of course, since it obviously "lugged" the engine. You are Instructed to drive as much as possible in overdrive for the same reason. Rather than recommend a specific gear to drive in, I think that its more reasonable to drive at a comfortable engine speed range between 2000 and 2500 RPM.

Our Honda Accord has developed a couple of annoying noises when we drive it at relatively low speeds. It is a 1990 model with an automatic transmission and a four cylinder engine. The first noise is a buzzing sound that seems to be coming from the exhaust system as the engine is accelerated at a moderate rate. Once the engine gets past a certain speed, the buzzing goes away. The second noise a kind of moaning sound that happens at a steady around-town speed but than it goes away as the car goes up to highway speed. Our regular mechanic couldn't find a cure so we took it to a Honda dealer's shop where we were told that it's a characteristic of the car. We were also told that their was a factory kit that can be installed that's supposed to fix these noises but it isn't always successful. P.H. Seattle, WA

A. Your Honda dealer is telling it to you straight. Honda provides an exhaust system fastening kit for the center section of the exhaust pipe that is supposed to cure it but mechanics tell me that it doesn't work all that well and it's kind of an expensive experiment. Your '90 is too old to qualify for a free fix so I think your dealers's shop is smart in not selling you a job that may or may not work.

Q. I have a 1990 Nissan 300ZX Turbo which I drive pretty hard. That's why I bought it. And while I drive it hard, I don't think I drive it hard enough to go through four clutches in nine years. I don't slip the clutch when I'm taking off or abuse it by shifting down without bringing up the engine speed at the same time. Each time the clutch has been replaced, the old one has come out badly burned and scared. I've had to have the job done enough times now that I recognize the symptoms and it's getting ready to fail again. Is there anything that I can do to get more life out of this expensive job? P.O. Eugene, OR

A. Although by your own admission, you drive the car hard, it sounds like you're heads-up enough to avoid expensive problems brought about by dumb driving techniques. Nissan has a redesigned clutch master cylinder and pedal return spring kit that may not eliminate the problem entirely but at least it will prolong the agony by a few years. The new version locks up the system more completely and gives enough "free-play" to the clutch to keep it fro slipping even a little when the pedal is released.