Many modern cars are fun to drive and the controls work seamlessly. Every time I drive one, I feel thankful that I’m living at the beginning of the electronic age. But, like any success story, there’s always a darker side. Electronic components tend to fail without warning, and they’re often as likely to fail at the beginning of the vehicle’s life as they are after a few years.
These thoughts crossed my mind the other day when a BMW 320i was brought in suffering a rough idle. August, our young, “modern” mechanic, was given the job card and I fully expected him to haul out some electronic testing equipment, but he didn’t.
He started the engine, let it idle and then approached it with a small can filled with light oil. He applied a drop of oil to various points on the intake manifold where there might be an air leak. When this was done, he used the same technique on the fuel-injection rail and struck it lucky when he applied a drop of oil to number three cylinder’s fuel injector. As soon as the oil hit the side of the injector body, the engine smoothed out for a second or two. “The oil will seal the air leak for a second or two,” he said and proceeded to undo the rail and lift it off with the injectors. The latter aren’t screwed in, but are press-fit into machined holes in the manifold. He inspected all the O-rings around the injectors and saw that the number-three ring was cracked. It could have been damaged during installation and the crack would have grown with time. We found a similar O-ring on a BMW that would have been in the shop for a few more days and used it to repair the damage.
It turns out that I needlessly blamed the electronics…
