Why Do Cars Stall?


Hopefully this doesn’t happen to you often, because when cars stall, the inconvenience can become a big deal in a hurry.  The infamous and often overeager Check Engine Light (CEL) may not even signal trouble, which makes matters all the more confusing.

There’s no single reason why it happens, nor can we present a definitive, all-inclusive list with any degree of brevity.  But there are some reasons that serve as a starting point.  We’ll focus on fuel-injected cars this time, which account for the vast majority of daily drivers on the road as opposed to older-style cars with carburetors.

Maintenance needed.  Cars today require less maintenance than ever, but a care and feeding regimen is still required beyond changing oil.  Stalling can occur when less frequent action items need cleaning or reach the end of their service lives.  It may not be a single item, but a combination that cure the issue.

Start with simple things like replacing the air filter and go from there.  Things may progress to the spark plugs and wires, replacing the oxygen sensor or cleaning the mass airflow (MAF) sensor.  Even items you wouldn’t normally associate with stalling, such as an automatic transmission fluid and filter change, can factor in.  Check your owner’s manual to identify any of these or other overdue maintenance items.

Repairs needed.  Even with perfect maintenance, car components can still wear out and fail.  Some of the aforementioned underhood items like the MAF can either be non-serviceable (unable to be cleaned and reinstalled) or are too used up to be useful.  This can also include the idle air control (IAC) valve, throttle body or ignition control module.  Leaking or missing vacuum lines also make cars stall, but replacing them is no major issue.  A more serious and expensive matter could be a plugged catalytic converter in the exhaust system.

Fuel-related.  The dreaded “bad tank of gas” doesn’t happen often, but it is possible and can make your car stall.  You’ll probably get some warning in the way of engine sputtering and hesitation first.  A bottle of fuel treatment can help if the issue is minor and tied to excess moisture in the tank.  If not, take note of the fuel level.  Too little can overheat the fuel pump and cause failure.  When running on “E” is not a frequent habit, you could simply need a new fuel filter.

Driving habits.  Identify if any of this is within your control.  You may not purposely stall your car, but some of what you do can contribute.  Pay attention to what’s going on when it happens.  Can certain weather play a part?  Will it only happen when you’re running multiple accessories like air conditioning, headlights and high-wattage sound system all at once?  Does it seem to be worse when the engine is cold or when it’s hot?  These answers can help a qualified technician better diagnose you car’s stalling if other means don’t.


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