Q. I have a 1999 Mercury Mystique with 80,000 miles. It runs well and has no problems until I have the oil changed. As soon as I get an oil change, the engine stalls while driving. This stalling will happen sporadically while driving and lasts one to two days. After a couple of days, everything is fine. I am due for an oil change; any suggestions?

A. The oil seems to be the only common denominator. Some Ford engines are very fussy about oil type and filters. This engine uses a variable camshaft requiring a specific oil filter and oil. The Ford filter has an internal check valve that keeps the exhaust valve closed when starting to prevent stalling. This next oil change ask the garage to use 5W-20 weight oil with a factory style filter.

Faulty fuel gauge sensor

Q. Is there a gasoline additive that can clean the fuel gauge sensor? The gas gauge on my Chevy Tahoe always displays “empty” regardless of how much fuel is in the tank. I was told that the problem is caused by a chemical build up on the sensors. I’m trying to avoid the expense of removing the gas tank.

A. If the gauge always shows empty, I would check the gauge circuit first, and then move on to the sensor. You are correct that in many cases the fuel level sensor fails due to the deposits in some gasoline formulas today. The sensor is not serviceable and will need replacing. There is some good news, however; unlike many vehicles, this sensor can be bought separately from the fuel pump.

Check the ignition coil

Q. We have a 1998 Toyota Camry with 165,000 miles on it. We love the car and haven’t had trouble with it until this past winter when it began to stall. Usually this would occur in traffic. Other times I would have difficulty starting the engine. I have had the oxygen sensor and the fuel filter replaced. These repairs worked for a while but it began stalling again. The mechanic suggested that it could be that the idle air control motor needs replacement. He weren’t sure if that was the problem, however, and we didn’t want to spend $800 and fail to solve the problem. The Camry has not stalled since the weather got warmer. Do you have any suggestions about what it could be?

A. There are three areas to investigate. The first is the ignition coil; many of these coils fail with age and cause a similar symptom. The second is the coolant temperature sensor, and then the idle air control valve. Regarding the estimate on the idle air control valve, it seems a little high.

Don’t paint the plate

Q. Are there any restrictions on applying new green paint to my license plate, which is old and faded? I hate to get replacement plates because I only have one plate on my car now and am afraid the RMV will require two replacement plates. I have been warned I can’t get a new sticker with the plate in this condition.

A. As much as you like your single green plate, it will need to be replaced with two license plates if it is in poor condition. If you try to touch up the numbers with green paint you will stopped and possibly ticketed for “altering” a license plate. It is not just the green characters but the reflectivity of the plate as well. The RMV is replacing single green plates at no charge to motorists who would like or need new plates. To be prepared, loosen the license plate screws before you go to the Registry.