Car’s Problem Does Not Compute
Question: I own a 1988 Pontiac Grand Prix that stalls when the car idles a long time in gridlock freeway traffic. I’ve talked to my dealer and he says nothing mechanically is wrong with the car. The computer shuts off the engine automatically when the catalytic converter reaches a high temperature. If the computer turns off the engine, why does it allow me to restart it immediately? The converter must still be at the same temperature.--J.H.
Answer: The dealer was completely misinformed about the computer shutting down the engine if the catalytic converter reaches a high temperature.
More likely, the dealer was concocting an explanation for something he does not understand. You have a potentially difficult to solve Catch-22 type engine problem.
Modern automobiles, including General Motors cars, have built-in diagnostics systems, in which a central computer detects when certain parts malfunction and can notify the driver through a check engine light on the dashboard.
But what happens when the computer malfunctions? Your GM computer may not know it is sick and it thinks it is doing you a favor by shutting down your car on the freeway.
Unfortunately, the built-in diagnostics systems offered by car manufacturers so far have not been able to diagnose a faulty computer. It is even difficult for mechanics to check a computer, especially if the problem is intermittent.
You need to find an enlightened dealer who is smart enough to call GM’s technical service organization. One bit of caution: You should exercise to absolutely refuse to pay for a new computer on a trial-and-error basis. It could cost hundreds of dollars and it may not fix the problem.
Q: A neighbor who has about six cars parked next to my bedroom window starts the cars at very odd hours. Two of them are Mercedes-Benzes with diesel engines. He warms them up anywhere from 10 minutes to a half hour and even revs them up. He claims it will put too much stress on the engines if he does not warm them up. How long is it necessary to warm up a car?
--B.M.K.
A: Not only is your neighbor inconsiderate, but he is probably doing more damage than good to his cars by long warm-ups.
Most automobile manufacturers recommend very short warm-ups during summertime temperatures. That means that you can begin driving, though gently, as soon as the engine is running smoothly.
Toyota, for example, specifically cautions against lengthy warm-up idling and against any other long engine idling. General Motors cautions its owners that long idling poses a health risk from the possibile carbon monoxide poisoning.
Engine oil begins to flow almost immediately after you start an engine. Within a minute, oil pressure should be stabilized. There is little or no benefit to waiting until the engine has reached operating temperature before starting out.
In very cold subfreezing weather, a slightly longer warm-up is a good idea. But once the engine has idled for a few minutes, it should be safe to begin driving.
The practice of revving a cold engine is potentially very harmful to an engine. By racing the engine at high speed, your neighbor is subjecting the engine to a maximum of wear and stress.
