A Sooty Mark on Dealer Diagnosis
Question: I was wondering why my car has to have spark plugs put in every two weeks? The plugs are coated with black soot and black soot also comes out of the tailpipe. It uses a lot of gasoline for a four-cylinder car. The “check engine” light comes on, but the diagnostic computer at the dealership says there isn’t anything wrong with the car. But I know there is. The car is a 1981 Chevrolet Chevette.--T.L.
Answer: This is another case of people needing to be smarter than computers. Unfortunately, too many mechanics are either incapable of knowing how to use modern diagnostic equipment or they don’t have the mechanical skills to outsmart a computer when it is wrong.
The symptoms you describe point to a classic case of the engine getting too much fuel. The sooty spark plugs are an indication of unburned or partially burned fuel. The black soot coming out of the exhaust pipe is a telltale sign.
Your problem seems to be so severe that it has even degraded your fuel economy. If the engine is getting too much fuel and not completely burning it, then you obviously are going to lose fuel economy.
One of the easiest ways a motorist can monitor the health of a car’s engine is to frequently check the gasoline mileage rate. A dropoff will let you know something has gone wrong.
There are plenty of causes of excess fuel being sent to the engine. If your car has a carburetor, the float could be stuck or improperly set. The carburetor could be otherwise fouled. The choke, which is supposed to give the engine more fuel when it is cold, could be stuck and flooding the engine with fuel when it is hot. The problem could be as simple as the air cleaner being dirty and clogged.
If the engine’s computer command system is triggering a “check engine” light on the dashboard, it could be indicating the source of the fuel problem or some other problem altogether. It could be that the fuel problem is causing a secondary problem that is being picked up by the computer. For example, the oxygen sensor could be coated with soot, which will trigger the check light.
Solving the problem should be relatively easy. The hard part may be finding a good mechanic.
Q: Please tell me if anyone makes a waterproof car cover. If not, what is the reason? C.C.R.
A: To my knowledge, a waterproof cover is not made. Most of the covers are nylon, cotton or a synthetic blend that allow water to soak in but also to evaporate through. The reason simply is that condensation would accumulate under the car and foster rapid corrosion. The best types of covers have a soft texture, but heavy body. They should be thick enough to block the sun’s ultraviolet rays.
