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Sensors Don't Replace Good Mechanic

July 24, 1986|RALPH VARTABEDIAN | Times Staff Writer

Question: I own a 1982 Pontiac J2000 with a sporadic but chronic problem. After running for about 30 minutes, the engine dies when coming to a stop. This is accompanied by a vibration noise somewhere between the engine and front seat. It takes three to four attempts to restart the engine. It's been to an independent service garage twice and the dealer three times. It's been computer checked but it keeps coming up "no code." Can you offer any suggestions?--J.L.

Answer: The one observation I would make on your problem is that all the modern computerized diagnoses don't take the place of even one knowledgeable and intelligent mechanic.

Automobile ignition and carburetion systems have gotten tremendously complex in recent years to satisfy emission and fuel-economy laws, but the majority of problems these engines experience aren't much different than they were years ago. The fuel/air mixture is either too rich or lean. The ignition timing is off. Spark plugs become fouled.

The problem is that all of the auxiliary systems make it virtually impossible to diagnose these simple engine problems without a lot of testing.

General Motors has gone heavily into built-in computer diagnosis of its engines. For example, your car has a so-called self-monitoring system that senses various engine conditions, such as the electrical voltage, engine temperature, water temperature and so on.

If the electronic controller that monitors all of these sensors finds a problem, it can signal the condition on the "engine check light" on the dashboard. Although most motorists aren't aware of it, the light can flash in various sequences to signify what the problem is.

When the light flashes once, then twice and then once, you have a 1-2-1 code. It means that everything is OK. That apparently is what your sensor is doing. More and more codes are being added all the time by General Motors. A sequence of one flash and then four flashes signifies the coolant temperature is low.

But if the electronic control module doesn't find any measures out of specification, then it obviously can't make much of a diagnosis. Its the old computer problem of "garbage in, garbage out."

Your problem is a good example of something that only an intelligent mechanic with a good working knowledge of the J2000's engine can properly handle. I suggest you take the car to a different dealer, and look for a mechanic who knows how to take his diagnosis to the next step. It's a real cop-out for a mechanic to say simply that the engine was a "no code."

Q: We own a 1973 Dodge Monaco station wagon with a 400-cubic-inch engine and an automatic transmission. A year ago, we parked on a steep incline with the shift lever in park. When we left, we had to pull the lever quite hard. Ever since, the transmission makes a grating noise when accelerating hard from a stop. Could this develop into something serious?--C.L.C.

A: It's never a good idea to allow the weight of a car to rest on the parking lever. On a steep hill, always set the parking brake first, then put the transmission into park. When starting out, put the transmission in neutral before releasing the parking brake.

Possibly, you damaged the transmission pawl, which is a shaft that holds the car in park. If so, you can repair that without overhauling the entire transmission.

But you may also have a problem with bad engine mounts, a fan contacting its shroud or a slipping transmission band. All these cause grinding noises like those you describe.

Q: I bought a brand-new 1986 Camry on March 1. The car performed well, but it began to develop a grinding noise when I pressed down the clutch pedal with the transmission in neutral. I found that if I did not press the clutch all the way to the floor, the grinding noise would not occur. The noise has been intermittent and has not occurred in the last week. What caused it?--R.C.

A: I am inclined to say your clutch is out of adjustment, but your Toyota has a self-adjusting hydraulic clutch. It's unlikely that the problem is with the clutch linkage itself.

You might have had a problem with the throw-out bearing inside the clutch mechanism, which is part of the assembly of friction plates that make up the clutch.

If the problem disappears, you'll probably never know what caused it. It isn't worth the trouble of tearing apart the transmission if everything is operating properly.

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