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When a Tuneup Wastes Time, Money

October 15, 1987|RALPH VARTABEDIAN | Times Staff Writer

Question: On the new fuel-injected automobiles with electronic ignition systems, what does a mechanic do during a tuneup besides change the spark plugs? At $40 per tuneup, I wonder what I am paying for.--S.T.

Answer: The tuneup cost covers a lot of things that you probably would just as soon not pay for, such as diagnostic computers at the dealership, higher labor costs and other charges that don't affect the way your car runs.

The advent of fuel-injection and electronic ignition has significantly reduced the amount of routine maintenance that cars need. The electronic ignition systems have eliminated points and condensers, as well as rotors and distributor caps in some cases.

Fuel-injection systems usually don't require any routine maintenance. But then modern carburetors don't have any settings that are routinely set by mechanics anymore, either.

What's left in parts replacement are spark plugs, gas filters and air filters. Ignition timing is still required, but some newer cars don't even require that anymore, because the timing is based on sensors that determine the position of the crankshaft. Idle speed is still one setting, however, that a mechanic adjusts during a tuneup.

Some imported cars use solid valve lifters, instead of hydraulic valve lifters. The solid lifters require periodic adjustment, typically done every 15,000 miles. This is quite an important item, because an out-of-adjustment valve can wear out or fail quite rapidly.

These overall improvements have meant that motorists no longer need the tuneups that were an annual ritual. The downside is that when an electronic ignition system, a fuel-injection pump or a computer module that controls all this stuff goes out, you are often looking at a repair bill that would equal the cost of tuneups for the next 10 years.

Q: I have a 1982 Mercury Cougar with a 200-cubic-inch engine. At 35 m.p.h., it goes into passing gear if I step on the gas pedal about one inch. The dealer can't help me. My A-1 mechanic says nothing can help me. The problem started last year. I have 67,000 miles on it. Can you help?--Frustrated Harry

A: The mechanics at dealerships are often at a loss in diagnosing transmission problems on cars with lots of miles because they do most of their work on new cars.

A transmission shifts gears when the engine reaches a certain speed. It also down-shifts when the engine is struggling under a heavy load. A transmission relies on engine vacuum to indicate that the car is under a heavy load and that a down-shift is required.

A common characteristic on old cars is that they have weak vacuum levels in all the systems that rely on engine vacuum. The vacuum, which is also used for a lot of other things, comes from the engine's intake manifold. When you push the accelerator down, the vacuum level drops. Vacuum is high when the engine is idling. As a car gets older and its vacuum level drops, the transmission is tricked into thinking the car is under a heavy load and down-shifts very easily. A further complication here is that Ford transmissions generally require a lot of vacuum.

One solution is to find a top-notch transmission mechanic to look for a possible vacuum leak. Or your engine may be wearing out, resulting in low vacuum levels. Another solution is to find a new vacuum port on the intake manifold. The existing port is on a line that branches and may be bleeding vacuum off. Your mechanic may be able to find a port right off the manifold or carburetor that would provide the transmission with a more accurate reading of the engine's load.

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