Some of the most common causes for a car's stalling whilst driving include: a poor idle speed control, or ISC, system, low fuel pressure, loss of ignition and vacuum or EGR leaks. Diagnosing the specific problem should be a priority in order to get it fixed.
There are a number of things that can be done when a car stalls in order to identify and diagnose the problem. These include:
- Flooring the accelerator, if this leads to quicker engine failure, the likely cause is a lack of fuel
- Looking for black smoke from the tailpipe, indicative of an abundance of fuel or a lack of spark
- Noting whether the engine starts back up immediately after stalling, indicative of an electrical fault if it does, or a bad fuel pump if it won't
- Checking for correlation between the amount of gas and the occurrence of the problem; the fuel pump, if located in the tank, is likely to be the problem if stalling happens more when the tank is around one quarter full compared with over three quarters full
Another, lesser known cause for stalling is low quality gas. If the gas has been contaminated with water, for instance, the engine will stall when the water enters the fuel pump from the bottom of the tank. In this instance, providing there is not too much water, adding one to two bottles of alcohol will usually absorb and disperse the water.