Question: I have a 1984 Chevrolet Cavalier that works perfectly, except for the air conditioner. Every time we have it on, it sucks in fumes from the car or bus in front of us. The dealer does not have an answer. Any suggestions?--R.J.M.
Answer: The only practical solution is try to not follow any buses, because General Motors cars do not offer a separate control to shut off outside air.
The control panel for your air conditioning has two settings, "max ac" and "normal ac." The difference is the amount of outside air that is mixed into the air stream. On max ac, about 80% of the air is recirculated from inside the car and 20% is outside air. On normal ac, 80% of the air is drawn from outside and 20% is recirculated from inside.
Many other automobile manufacturers provide a separate control to allow the air-conditioning system to use all outside air or to only recirculate inside air. Recirculating inside air has the advantage of providing the maximum cooling power and keeping out fumes and dust.
You might want to run the air conditioner on the max setting all the time and simply select a lower fan speed to adjust the temperature inside the car. This should not increase the load on the air conditioner or affect fuel mileage.
Q: We have a 1985 Jeep Wagoneer that has had a new battery, new carburetor, new torque converter, new torque spring and a new transmission installed in the first four months of ownership. Now at five months, we have a differential oil leak. Also, there is a vibration throughout the car. What has caused these new problems, and are they related to the other problems?--T.B.
A: The vibration is probably not related to the leaky differential, though all of the problems you have had with the drive train seem to indicate that something overall is lacking.
American Motors has had reports of problems with differential seals leaking, and they have issued bulletins for procedures to fix the leaking. The fix is simply to replace the seal.
The vibration problem is somewhat more difficult to diagnose, but it could be traced to one of two areas. First, when your drive shaft was pulled out, it may have been installed in such a way that it would cause dynamic vibrations.
The procedure for fixing it involves rotating the companion flange, which, without a lot of technical jargon, is a part that connects the drive shaft to the differential gears. Even though the drive shaft is balanced, an incorrect orientation of the flange will cause vibrations.
Q: I bought a new Jeep Cherokee a year ago, and it ran fine all summer, spring and fall. Starting last December, the car had difficulty starting. Sometimes the engine would race for a few seconds and then die. After three towings to the dealership, the only recommendation was that I switch to premium unleaded fuel. That seemed to work, but I don't see why.--R.B.
A: I'll take your word for it that the higher-octane fuel solved your starting problem, but your car is designed to run on regular unleaded, and it likely has some other carburetion or ignition problem.
You may have a problem with a device called a chock assist on your Cherokee. It pulls the chock off when the accelerator is depressed sharply. If it doesn't work properly it will cause the engine to stall.
Ralph Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.