DEAR DOCTOR:

My brother owns a 1999 Cadillac DeVille. When he takes his foot off the gas pedal the engine will stall. The dealership has cleaned the carbon build-up, but the engine still stalls. There are no trouble fault codes in the computer. What are your thoughts? Joe

DEAR JOE: Go back to the dealer again and ask for a different technician to work on your vehicle, or go to an independent repair shop.

DEAR DOCTOR: With gas prices on the rise, I am always searching for ways to improve gas mileage. In addition to regular maintenance and driving habits, I am looking for ways to improve gas mileage. Some auto magazines have advertisements for fresh air intake systems. The advertising touts improved gas mileage and power. However slight, are they worth the investment? George

DEAR GEORGE: There is no question that a fresh air intake system will increase power at half to a wide-open throttle. A simple high performance air filter element in the stock air filter could be marginal at best. Anytime you get fresh cool air into the engine, it is a plus. As for the cost trade off, it will take a few years at least. The best solution for increasing gas mileage is proper maintenance, monitor tire pressure, avoid jack-rabbit driving, and use full synthetic engine oil.

DEAR DOCTOR: The Department of Transportation states that any tire over five years old should be replaced regardless of condition. Some tire manufacturers say this is not true, even if there are small dry cracks on the tire. This is a big discussion at work. What are your thoughts? Charlene

DEAR CHARLENE: My opinion is that any tire showing signs of dry weather cracking needs replacement. There are some cases in vintage and classic vehicles that have limited driving on weekends, car clubs events, etc., that the five-year replacement does not apply. For those who drive late model vehicles, pay very close attention to tire condition and age.

NOTE TO MY READERS: As a free service to the readers of "Ask the Auto Doctor," you may have your body shops and technicians receive no-cost diagnostic help from Identifix through June 30, 2007 utilizing the code provided in this column. Your service advisor may call 800/941-0186. Code: JDA12.