Dear Doctor: I own a 2003 Lincoln LS with only 4,700 miles.

The "service parking brake" message appears and the electronic park brake light stays on. The engine failure mode also illuminates. If I shut the engine off and restart it, the lights will go out. The dealer has checked the car on their computer and said there must be a glitch in the system. Could it be a bad computer? -- Peter

Dear Peter: Go to the dealer with the lights on. When you get to the dealership, do not shut the engine off. A technician can check the computer while the lights are on and determine when it came on and what driving conditions the car was in when the fault happened. The computer should retain a trouble fault code whenever the service light comes on for a pre-set period of time.

Dear Doctor: I recently purchased a new car and want your opinion on putting in an oil additive such as Prolong or Slick 50. -- Nate

Dear Nate: The automotive chemical market is a billion dollar market. All the commercials look great on TV. The fact of the matter is, I do not know what they do. Do I use any of these products in my vehicles? The answer is no! Do I recommend them to my customers or sell them? No! I do not see a need for any oil-enhancing products on good running engines or transmissions.

Dear Doctor: I own a 2000 Volkswagen Passat turbocharged 1.8-liter four-cylinder with 82,000 miles. When I pull up to a traffic light and let the engine idle for a few minutes, the engine seems to vibrate and wants to stall. The idle goes up and down. If I put the transmission in neutral, the problem goes away. I asked my mechanic and he says he would have to put it on a computer. What do you think? -- Elmer

Dear Elmer: An uneven idle can be caused by a number of things, including chronic problems with mass airflow meters, ignition coils, and small vacuum lines that break by the throttle body. If someone replaces the battery, the computer will need to be reprogrammed. I would suggest using a technician with VW experience.

Dear Doctor: I own a 1994 Chevrolet Classic 5.7-liter V-8 with 155,000 miles. The engine sometimes stalls. If I let it sit for a minute or so it will start up and run fine. It recently had a complete tune-up, but this made no difference. -- Stewart

Dear Stewart: Has anyone checked for trouble codes in the computer and/or fuel pressure and volume? The front mounted distributors have been troublesome over the years and expensive to repair and replace.

Dear Doctor: I own a 1997 Oldsmobile with 108,000 miles. Recently it developed an intermittent stalling problem. It doesn't matter whether it's at idle or moving. Yet it always restarts. The technician hooked it up to the computer scanner and came up empty. -- Joe

Dear Joe: Have your mechanic get in touch with Identifix by going to www.idenitifix.com to learn about problem areas with the stalling condition you have. The list of possibilities that could cause the stalling is long.

Dear Doctor: I own 2004 Chevy Blazer 4.3-liter V-6 2WD with 5,500 miles. My problem is poor gas mileage. In warm weather on the highway, it gets 16-17 miles per gallon. In cold winter months the mileage drops down to 12.5 mpg. I have been to three dealers and they all checked it on their computer machines and said there is nothing wrong. I also own an old GMC Jimmy with 160,000 miles that still gets a lot better gas mileage. -- Ken

Dear Ken: Many SUV owners are complaining about poor gas mileage. Some of the newer trucks like yours do use more gas than the older models. Strange as it may seem, they also burn that gas a lot cleaner. If there was a problem with any part of the fuel management system, the 02 sensors would set the "check engine." It takes 5,000 to 7,000 miles for engine break-in.

Dear Doctor: I own a 1998 Mercury Grand Marquis with 120,000 miles. Once a month I start the engine and release the gas pedal, and the engine will stall. It will restart instantly and run fine. Sometimes I pump the gas pedal and it will stay running. The mechanic checked the computer and said there were no trouble codes. What do you think? -- David

Dear David: The one common problem I find with Ford products are dirty mass airflow sensors. This can cause running problems such as yours without setting a "check engine" light. I suggest a full engine diagnostic exam, including a check of pending codes, fuel pressure and fuel volume. You may also suggest that your repair shop contact Identifix at (800/288-6210) to set up an account. Identifix tracks repair history and problems of vehicles all over the country.

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