Q. I own a 1993 Ford Mustang LX 5-liter with a 5-speed transmission. It is a kick in the pants to drive, but I don’t like the hard ride. Just about everything mechanical in the car has been replaced or repaired but the ride is still just too hard for me. What can I do to make it ride better to suit my 51-year-old lower back?
T.T., Chicago
A. The thing that can change the ride significantly are ride-control devices–shock absorbers and struts. If you have changed them, we would advise one of those viscoelastic (memory foam) seat cushions, the kind often advertised showing someone’s handprint left in the foam. Brookstone, among other places, sells them.
Q. Why do the starting problems associated with winter-blend gasoline in the spring not happen with the switchover from summer blend in the fall?
M.J.G., Chicago
A. The problem with winter blend gasoline is that, on the occasional warm spring day, it vaporizes prematurely. That causes drivability problems. In the fall, on a cold day, it may take a wee bit longer to start the engine due to the fuel’s lower volatility, but seldom does it cause stumbling or hesitation because the fuel does not vaporize until it leaves the injector.
Q. I asked the Volkswagen dealer to check my car due to a tingy noise (sounds like a piece of rust or stones are bouncing around in the catalytic converter). The dealer did a diagnostic and nothing came up. Every time I push in the clutch, the noise goes away. But when I release and accelerate, the noise appears. You can hear it inside the car and outside the car. What is causing it?
J.G., Chicago
A. What you describe is the sign of a bad throw-out (release) bearing. It may be worn out or lack sufficient lubrication. This is something that won’t show up on the computerized diagnostic equipment. Replacing the bearing is the only solution, and we suggest replacing the clutch at the same time if it has high mileage on it.
Q. You have written about the differences between diesel and gasoline internal combustion engines and have also addressed the causes of diesel pollution. But what is the source of the extra racket?
N.P., Chicago
A. Diesel engines do not use spark plugs. Instead, they operate by compressing air in the cylinders to a ratio of 20:1 (or higher), double that of the normal gasoline engine. The extreme compression makes the air so hot that, when fuel is injected, combustion occurs.
“In older diesel engines, pressure in the fuel lines opened spring-loaded injection valves at about 4,000 psi and the sudden injection of fuel into the cylinder caused a steep pressure rise to suddenly build in the combustion chamber,” said Al Krenz of Robert Bosch, which makes diesel components. “Sounding much like a series of small explosions, these were heard as diesel rattle.
“Modern electronically controlled diesel technology uses pre-injection pulses and `shapes’ the main pulse, so the sudden pressure rise–and the diesel rattle–is virtually eliminated,” Krenz said.
Q. I have 1998 Toyota Corolla with 77,000 miles on it. How often should I change fuel filter? It is about 25,000 miles since the last time I changed it.
C.S., Mt. Prospect
A. Most carmakers do not specify a fuel-filter replacement schedule, but we usually replace ours at 50,000-mile intervals. However, a spokesman from Fram, a filter manufacturer, told us they suggest every 36,000 miles. Of course, we also would change the filter whenever any fuel-system repairs are performed.
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Bob Weber is an ASE-certified Master Automobile Technician, having recertified every five years since 1978. Address your technical questions about cars and trucks to him in care of Motormouth, 17717 Silcott Springs Rd., Purcellville, Va., 20132. Send e-mail, including name and town, to motormouth(underscore)trib@verizon.net. Answers will be supplied only through the newspaper.
