Every great mechanic has a little Mr. Spock in him. There are lots of technicians who are quite capable of replacing worn or defective parts competently, following outlined procedures successfully. But the truly great mechanics , the ones who find and solve the problems others can’t or won’t, all follow the ruthless logic of Mr. Spock, tempered with an occasional burst of intuition from his human half.
I recall back in the early eighties a customer complained of an engine stalling condition. This was in the day when the Sun oscilloscope was the king of diagnostic equipment, giving a trained observer a window into all aspects of engine performance, and we found nothing. Repeated short test drives failed to duplicate the symptoms. With further interviews we learned that the problem didn’t occur until the car had driven some distance, and had fully warmed up.
At this point we needed to experience the stall. The car was left for the day and I drove it every chance I got. Finally, coming to a stop light on my fifth test drive, the engine shuddered hard, and as the car stopped, the engine died. Now blocking traffic, I threw the shifter into park, and thankfully the engine re-started with no problem. And stalled the second I put it in drive.
After repeating this several times I realized that the transmission was “locked” in some fashion, sort of like dropping the clutch on a manual shift at a stop in high gear. Eventually I was able to get going again, having had my introduction to the “locking torque converter.”
In short, the automatic transmission works because of a device called a torque converter. This is what allows you to sit still with your foot on the brake without stalling the engine. A drum full of fluid transmits the power from the engine to the transmission without the components ever being in physical contact. There is a loss of efficiency, say 10% at the max, but when gas was cheap, fuel standards not in existence, and engines had power to spare, who cared?
But all that changed in the eighties. The locking torque converter using hydraulic or centrifugal clutches allowed a solid coupling between engine and transmission once the computer determined proper temperature, gear, and road speed had been achieved. The problem was, a sticky or clogged solenoid wasn’t allowing the converter to “unlock” when slowing down and stopping, thus stalling the engine exactly as if you had stopped a manual transmission car without pushing the clutch. Simply unplugging the connector, which thankfully controlled nothing else, confirmed the problem.
Within a year there was a major GM tech bulletin concerning the issue, but we didn’t have the benefit of that knowledge when we figured it out. “Once you have eliminated the impossible, whatever remains, however improbable, must be the truth.” I actually think Sherlock Holmes said that first, but he wasn’t in my living room seven nights a week like Spock.
That little story is baby stuff compared to what our techs have to deal with now. Up-to-date information is far more accessible than ever before, but cars are a thousand times more complex than they were in my heyday. Radios that cause a car not to start (seen it). Defective light bulb causing the traction control system to shut down (seen it). Placement of the inspection sticker causing the automatic lights not to work (!) (seen it!).
I am impressed every day by our technicians’ ability to use logic to solve seemingly unexplainable problems. I hope you will be too. Long live Spock.