It seems impossible to stall my 2010 Volkswagen Scirocco when I start the engine from cold, but after being on the road for a while the engine sometimes stops when I am pulling away. As you can imagine, this is particularly dangerous on roundabouts. What’s going on? MR, Penzance
This may be less a fault than a peculiarity of the sort of engine management system found in many modern cars, which attempt to make them as fuel-efficient as possible. Fortunately, it is possible to adapt your driving style to overcome the problem.
Your car’s engine management system relies on a number of sensors to indicate the precise ratio of fuel to air entering the cylinders at any time. When the engine is warming up, the mix is richer, with proportionally more fuel to air (the equivalent of pulling the choke on an old car, now managed more precisely by computer). At this point, as you have found, your car is hard to stall.
When the engine has warmed up, the proportion of fuel drops, and when the car is idling the engine will run particularly lean — that is, with the minimum amount of fuel needed to keep it ticking over. What I believe is happening is that the computer is not responding quickly enough to the sudden change of circumstances when you go from idling at the entrance to a roundabout to pulling away. For a second or so the engine is not receiving enough fuel to manage the sudden heavy acceleration demand, and so it is more likely to stall.
This is a problem reported by drivers of many modern cars, though most eventually adapt their driving style to compensate, often without even realising it. The solution is simply to apply slightly more throttle than usual when you are setting off.
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory – read more from Dave here.
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