My two-year-old Fiat 500 stalled when I'd stopped suddenly in stop-and-go traffic to let another car merge. The guy behind me honked like a maniac and then pulled around (there were two lanes) and gave me the finger. I understand his frustration — new cars with automatics aren't supposed to stall, right? I Googled it and got everything from low transmission fluid (mine's fine) to a sensor failure to major engine damage. This was a month ago and it hasn't happened since. Here's my question: do cars ever just stall, or it always the sign of a major problem? — Derek, Vancouver
Sometimes, a random stall is just a random stall.
"If you have a smart phone, I'm sure you've had it shut down randomly by itself and then you restart it and it works fine," says Dave Weatherhead, automotive professor at Centennial College in Toronto. "With so many systems in a car integrating together, you could get a random blip that caused it to stall and it might only happen that once."
There are a lot of reasons a car might stall just once — software glitches, a bit of water or air in the gas tank, or even a magnetic disturbance, Weatherhead says. To narrow it down would require a cry-stall ball.
"It really could be anything — in my opinion, a single stall with no check engine light is not really cause to go back to the dealer," Weatherhead says, "If all the systems are working fine, they'll come back with no fault found — the only advantage is that then the complaint will be lodged on your record and that could help you if it gets progressively worse."
But, if your engine stalls again, it could signal a chronic problem. You should bring it into the dealer.
"I've had my own vehicle stall randomly, but if it's happened three, four, or five times, bring it in," Weatherhead says, "It could be a chronic problem, like GM had with those ignition switches— I can't tell you how many of those I had to replace."
Bringing it in after just one stall might not give you any answers, but the cost of the check should be covered by warranty, Weatherhead says.
Often the software will shut down the engine as a protective measure when a potential problem is detected, Weatherhead says.
"If it's an issue with a sensor shutting down the engine, that code should be recorded by the computer," he says. "But if it's a non-controlled stall and you can't duplicate it, it's one of the hardest things ever to diagnose — if it's once every six months while you're turning left during a full moon, it's tough to find unless you stumble upon it."
It can take sleuthing – and luck – to figure out the cause.
"I had one in front of me that some times you could run it for an hour an it would suddenly quit and other times it would stall as soon as you started it," he says. "It ended up being a cracked computer motherboard. Random vibration was causing a break in the circuit."
Google and chat rooms can only take you so far in figuring out a diagnosis, but it's a good way to find out whether others are having the similar problems with the same vehicle.
"If you're car stalls once, don't panic. If it happens again bring it in," he says.
If you have questions about driving or car maintenance, please contact our experts at firstname.lastname@example.org.
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