Auto Start/Stop
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Newbie
Joined: Oct 2024
Posts: 11
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Auto Start/Stop
Hi. I am curious why the start/stop feature seems to be a little quirky. When approaching a red light, for example, with traffic in front of me, the start/stop activates and the engine stops, but while sitting there waiting, it will start again and idle. Nothing changed and car in front did not move. From what I understand from the manual, this shouldn't be happening. Any ideas?
Out Of Control!!
Joined: Nov 2018
Posts: 11,400
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From: San Francisco Bay Area
2019 C63CS
The system monitors various parameters and if any become unfavorable then the engine is restarted. A big one is interior climate. When the engine is off, the AC compressor doesn't run and the engine starts to cool down, so the interior will start to warm up in the summer and cool down in the winter causing the engine to eventually restart to keep the climate around the desired temperature. Also, the longer the engine is off, the more time the oil has to start dripping down into the oil pan and leave parts of the engine insufficiently lubricated, so the engine restarts to keep it lubricated. Similarly, the coolant starts to cool down and the engine falls out of the ideal temperature range for combustion, which would ultimately worsen emissions again once it restarts. So it's all a balance of keeping the engine off to reduce emissions, but not too long to increase emissions unnecessarily when restarting and make the interior unpleasant. You'll find that on days where it's really hot or really cold outside, the engine will restart more frequently to keep you comfortable.
Last edited by superswiss; Nov 1, 2024 at 02:20 PM.
Thread Starter
Newbie
Joined: Oct 2024
Posts: 11
Likes: 1
Thanks for the explanation. Makes sense. I thought it likely was do to climate control as when it restarts it does so less than a minute after it shuts down. The weather is hot here most of the year, so given what you're saying the start/stop feature would be basically useless in this climate......
