Q. The "check engine" light has been on ever since I purchased my 2003 Hyundai Tiburon (99,000 miles, four-cylinder). The dealership has replaced both catalytic converters, the oxygen sensors and the exhaust flex pipe. After all this, the "check engine" light came back on for a code pertaining to the oxygen sensors. What could be the problem?
A. There are two things to look at. First, it is not uncommon for the exhaust manifold to develop a slight crack that will set this code. The second possibility is a poor ground connection. Check the electrical grounds, especially where the alternator mounts to the engine.
Q. I have a 1997 Toyota Camry with a four-cylinder engine, and I am concerned about the timing belt. The car has 65,000 miles on it. Some people tell me I should change the belt now; others say it is not due until 90,000 miles. Could you give me the correct advice?
A. On 1997 and older models, under normal service conditions, Toyota does not recommend a specific maintenance interval. On 1997 and older cars driven at low speeds, or vehicles that idle for long periods of time, Toyota recommend the timing belt should be replaced at 60,000 miles. Starting with 1998 models, Toyota recommends the timing belt be replaced at 90,000 miles or 72 months, whichever comes first. Considering the change in Toyota's recommendations and the low mileage in your car, I would consider having the timing belt replaced.
Q. I have a 2007 Toyota Highlander with a four-cylinder engine. So far, I have only put 8,000 miles on it. Is it necessary to put any additive in the gas to clean the fuel injectors? I always used Lucas fuel-injector cleaner in my old car in every 3,000 miles; is it necessary in my new vehicle?
A. Gasoline sold today has sufficient additives to help keep fuel injectors clean. Using an extra additive won't hurt, but it may just be money spent unnecessarily. If you check the vehicle's owner's manual, you won't find any reference on a fuel additive as a required part of any service.
Q. I am planning to replace the timing belt on my 2001 Volvo V70 Turbo. At the same time, I would be replacing the water pump. The job doesn't look too difficult, but I would like your opinion on whether I should tackle this. I am sort of handy and have replaced timing belts in other cars. It looks like it would be a good spring-time project. What do you think?
A. Since you need to remove the timing belt when you replace the water pump, it makes sense to do both at the same time. According to the flat rate time guide (the reference guide that professional repair shops use to calculate labor times), the job can be completed in a little over two hours. The minor problem is there are two specialty tools required to complete the job. If getting the tools is not a problem and you take your time and have a good reference book, it should be a fun job. One warning: As you are working on the engine, be extremely careful not to rotate the camshafts or crankshaft with the timing belt off or the engine could be damaged.
Q. I change the oil in my car every 3,000 miles, but lately my life has gotten so hectic I'm having trouble finding time to get the oil changed. How necessary is it to change the oil in my car every 3,000 miles? I drive the car every day and it's important to me that it is well maintained.
A. In years past, the 3,000-mile, three-month oil change was the standard. Over the years oil, oil filters and engine design has improved. Changing a vehicle's oil at 4,000 or even 5,000 miles is certainly acceptable. This doesn't mean you should ignore what is going on under the hood. On a regular basis, you should check all the fluid levels and add to any that are low. You should also never exceed the manufacturer's recommendations.