The Car Doctor

Unfiltered air, timing belts, transmission overhaul

By John Paul, AAA Car Doctor
July 3, 2008

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Q. My husband has a 1999 Chevy Malibu. It's been over a year now that the heat or air conditioning won't blow at the floor, but comes out on top. I turn it to the down arrow but it just comes out of the top vents. Do you know what would cause this and would it be a costly repair?

A. The problem is more than likely related to a vacuum leak in the heater vent system. The airflow is controlled by a series of vacuum actuators. The problem could be one of the actuators or a leak at the vacuum tank or vacuum line.

Q. This is a long story, but I had to have a used engine put into my 2003 Hyundai Elantra. When trying to replace the air filter the other day, I noticed it wasn't dirty at all; it actually looked as clean as the new one I had just bought. While replacing the front headlight that burned out, I noticed a long black plastic hose between an open space of the battery and rear part of the front headlight. It was under the battery cover, so it wasn't visible at all whenever the hood was open. It seems to be that this is the fresh air intake for the engine. Could this be a problem since none of the air is getting filtered? This has been going on for 14 months. Should I replace the car or is there nothing to worry about?

A. Certainly, driving around with unfiltered air going into the engine isn't healthy but it shouldn't have caused enough of a problem to trade the car. I would suggest a thorough cleaning of the throttle body and fuel intake system as well as an oil change.

Q. My 2000 Chevy Suburban will not start. I tried to jump it but got nothing. There is plenty of electricity, and the radio and interior lights all work. Two days ago it would only start with a jump. Help!

A. I would start with a basic check of the electrical system. A shorted battery, corroded cables or worn starter could be the problem. A technician can quickly and accurately test the battery, starter and electrical connections to determine the problem.

Q. Will the engine be damaged on a 1997 Ford Escort LX if the timing belt breaks? It's never been replaced and the car has 119,000 miles.

A. The engine in your Ford Escort will not be damaged if the timing belt breaks. Since your Ford is 10 years old and has 119,000 miles on it, I would suggest replacing the timing belt. When it does break, the timing belt will fail with no warning and leave you stranded. The typical cost to replace a timing belt on your car is $250 to $300.

Q. My 1991 Nissan Maxima with 98,000 miles has recently been having a problem with the transmission. When I need to pass on the highway, the transmission does not shift from fourth to third gear, but waits till I hit 5,000 or 6,000 rpm to downshift. But if I drive aggressively it downshifts. Do you think my transmission is worn out?

A. The problem could be related to the speed sensor or throttle sensor. However, depending on how long the transmission has had this problem and considering the car is 16 years old, it is possible at some point the transmission may need a complete overhaul.

Q. My 1998 Mazda Protege with 81,000 miles has a problem with an intermittent "check engine" light. It will come on after I gas up or when we have a few days of rain. I have had my mechanic and other auto places check it, and nothing shows up on the computer diagnostic machine. I am 70 years old and it makes me nervous to drive the car with that light on. Why doesn't the problem show up when it is tested?

A. If you are able to bring the car into the garage when the light is on, the repair shop should be able to find the cause of the "check engine" light. Once the code is determined, then the car can be repaired properly. The two most common problems are with the exhaust gas re-circulation valve and the mass airflow sensor. Both these parts could turn the light on without causing much of a drivability problem.