subject: Identifying The Cause Of An Engine Stall [print this page] Your car's engine can stall due to many factors, which makes it difficult to determine the root cause of the problem. Troubleshooting the issue starts with isolating when it occurs. For example, the engine might die after starting your car in the morning; it may stall out when you're waiting at a red traffic light; it can even die when you're driving, though this is far less common than the other two scenarios.
This article will take a closer look at the individual parts that can malfunction and cause your engine to stall. We'll approach the issue in three sections: after a cold start, while idling, and while driving.
Stalling Immediately Following A Cold Start
When your car stalls after having been cold started, the problem is usually due to one of two main factors: your engine is receiving an insufficient amount of fuel, or it is receiving excess air. There are several reasons either of these circumstances can occur.
For example, a sensor in your engine monitors the temperature of air passing through the intake valve of the cylinders. This sensor sends this data to your car's computer. The computer, in turn, calibrates the air-fuel mix based on this data. If the sensor malfunctions or reports inaccurate data, the resulting air-fuel mix in the combustion chamber may be made too lean. This can cause stalling.
The coolant sensor can have a similar effect. If it tells the computer the coolant is warmer than usual, the computer may deliver less fuel into the combustion chamber. This will lean out the mix, which might cause a stall.
If there is a leak that is affecting the compression within one or more cylinders, your engine may be unable to idle properly after starting. This often occurs when one of the valves fails to create a sufficient seal. If the compression leak is significant, your car might stall.
Another possible cause is worn spark plugs. If your plugs are worn to the point they cannot provide enough spark for ignition, your engine will misfire and likely die.
Stalling While Idling
Suppose you drive your car immediately after starting it, thus warming it up. You approach a red stop light and engage the brakes. Your vehicle idles for a moment while you wait for the light to turn green, and eventually sputters and stalls. In this case, the problem may be due to reasons unrelated to those described in the section above.
First, there may be a significant load placed on the engine. For example, your air conditioner's compressor might be creating an excessive drag.
Second, your battery may be run down, causing your alternator to work harder than normal to keep it charged. This can place an excessive load on the charging system, which, in turn, can create a drag on the engine.
Third, a number of circumstances may lead to the air-fuel mixture becoming too lean. As noted earlier, this can cause the assembly to stall.
Stalling While Moving
If your car dies while you are driving, the issue will likely be related to a lack of sufficient spark. Besides worn spark plugs, this can be caused by a malfunctioning crankshaft position sensor or a defective ignition switch. It is relatively easy to check for a spark, though you will need another person to help you; one person turns the engine over while the other person inspects the plug wire.
If the spark is fine, there's a chance the stalling issue may be due to a lack of fuel pressure. That means the fuel pump may be the problem. Check the appropriate fuse first, since a blown fuse is far less costly to replace than a faulty fuel pump.
An engine stall is frustrating, especially since it is often difficult to troubleshoot the issue. Be as clear as possible when describing the circumstances under which it occurs to your mechanic. That way, he'll have a better idea regarding how to resolve the root cause.
