Dear Doctor: My son owns a 1999 Saab 9-5 turbocharged four-cylinder with 92,000 miles. The car has a problem with gasoline evaporation from the fuel tank. The gas tank is plastic and I do not see any signs of leaks. What are your thoughts? -- Paul

Dear Paul: Today's cars have very tight fuel systems. There are many valves and hoses that connect from the gas tank to the evaporative system. We use a smoke machine to look for problem areas dealing with fuel system concerns like yours. Unless you find a qualified technician who has knowledge of the Saab, your best bet is the Saab dealer.

Dear Doctor: I own a 2001 Dodge Van 1500 with 26,000 miles. When I start it, drive it a mile and put it in park, I hear a knocking sound coming from the engine area. The noise goes away after an hour of driving. Any ideas? -- Al

Dear Al: Knocking sounds from engines and pulleys are often heard when the engine is cold. There are a variety of areas that can cause knocking sounds. You will need to bring the van to a shop so they can actually pinpoint the source of the knocking sound.

Dear Doctor: My daughter has left the country for a two-year assignment with the Peace Corps. She owns a 1998 Chrysler Sebring, which will be kept in the garage. What are your suggestions for long-term storage? Should I remove the battery or trickle charge it? What about tires and suspension? Should I keep the car registered and drive it weekly? -- Jim

Dear Jim: Long-term car storage needs to be taken very seriously. It starts with fluid replacement, such as brake, power steering, transmission, oil and filter, coolant, and gasoline treatment. These steps are critical to proper storage. It is also advised to pump the tire pressure up to the maximum air pressure listed on the outside of the tires. Other concerns are all the seals, gaskets, rubber belts and hoses, not to mention the tires drying out. If it were my daughter's car, I would either sell it or drive it weekly if at all possible.

Dear Doctor: I bought my 18-year-old daughter a new 2005 Chevrolet Cobalt that has been nothing but problems. The engine will stall out when making a left or right turn, especially at intersections. She has had four near-miss accidents. I have brought the car back to the dealer and they have not been able to find the problem. This is a safety hazard. What can we do? Lucille

Dear Lucille: This is a first for this stalling complaint. I would check with the dealer and the state for a lemon law buy-back. The dealer has a number of attempts to correct the problem within a certain amount of time and days out-of-service.

Dear Doctor: I recently purchased a 1997 Honda Accord with only 60,000 miles. The car had a louder than normal exhaust tone. The shop said it had a cheap replacement muffler. The engine also used a quart of oil on a recent 200-mile trip. Can the exhaust fail in this car so soon and what about the use of engine oil? Bill

Dear Bill: You have to remember the car had low mileage for the 1997 model year. This can present two problems. First, the water build-up in the exhaust caused the exhaust to rot from the inside out; second, the piston rings could be carboned-up as well. The cheap exhaust replacement is an easy fix with a factory replacement part. The oil consumption should be checked. I would check the ventilation system first. I would also use a decarbon treatment (the kind that goes directly in the cylinders) to help remove the carbon on the piston rings. Leave this service to a professional technician.

Dear Doctor: I am the owner of a 1995 Toyota Camry four-cylinder with 180,000 miles. The car has a rough idle in drive. In neutral it is hardly noticeable. I have had the engine mounts replaced, a full tune-up and the computer checked for trouble codes. Do you have any suggestions? Louis

Dear Louis: When any vehicle has a rough idle it is usually a sign of one cylinder not contributing like the others. This can be caused from a mechanical condition, such as valve or piston camshaft. There could be a vacuum leak, not fully seated EGR valve or dirty spray pattern fuel injector. Have a qualified technician perform an engine performance test. This should help him find the problem area.

Dear Doctor: I own a 1998 Honda minivan purchased new. The anti-lock brake light comes on and this has been an ongoing problem since the purchase. The dealer has never been able to find the problem. Do you have any suggestions? Joseph

Dear Joseph: Unless you have documents from the time you purchased the vehicle, you will be on your own for the repair. Whenever there is a trouble fault light, the computer should retain the failure information in memory for a certain amount of time. Any good repair shop should be able to retrieve trouble fault codes. -- Junior Damato

Send questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347