Why car stalls when idling

This is most often felt at low speeds and can lead to vehicle stalling. A problem with the solenoid can also be a reason why a car stalls at idle. Another potential transmission-related cause of car stall is low transmission fluid levels. The good news with such an issue is that it is very easy and inexpensive to fix. Just check the level of transmission fluid in the car and top off to the required level.

If your car stalls at idle, one of the possible causes is a problem in the idle air control actuator. This component is responsible for managing the RPM of the engine at idle speed. Unfortunately, if the actuator gets damaged, the engine will no longer receive signals that tell it at what speed it should operate when idling.

Hence, it stops. The same thing can happen if the system gets clogged. Excessive carbon buildup can also prevent the more accurate measurement of engine speed. This can also lead to a situation where the car stalls when stopped. For instance, a failing fuel pump will not be able to provide the engine with fuel from the tank.

This can lead to a reduction in fuel pressure, resulting in an inconsistent flow of fuel to the engine. At high speeds, this is not a problem. The problem occurs when the engine is running at low speeds.

A pause in the flow of fuel can kill the engine. Defective fuel injectors and low pressure fuel can also cause a vehicle to stall when it is running at low speeds or when it comes to a stop.

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There are three things an engine needs in order to run: fuel, air, and ignition. Ignition means spark, by the way. The problems that present themselves might be worse than a simple check engine light. A lack of fuel can be caused by a plugged fuel filter, dirty fuel injectors, or the wrong type of fuel in the tank. No word yet from Toyota of the cause, but it will probably turn out to be a PCM programming issue. One strategy for diagnosing a stalling problem that only occurs intermittently is to wait until the problem gets worse before you attempt to diagnose it.

It's always easier to find a part that has failed than to find one that works most of the time and only acts up occasionally. One time saving step that may allow you to zero right in on the cause is to check for any Technical Service Bulletins TSBs that might have been published by the vehicle manufacturer.

It may be a situation where there's a pattern failure and the manufacturer has already figured out the problem and posted a fix. The few minutes you invest in doing a TSB search can save you hours of frustration and wasted diagnostic time.

And with many late model vehicles, the cure is often a PCM reflash rather than replacing something. The next thing you should always do is hook up a scan tool and check for codes even if the Malfunction Indicator Lamp MIL is not on the lamp may be defective.

Look for history codes or pending codes that may shed light on the problem. Also, look at the sensor inputs to the PCM when the engine is idling both after a cold start and when it is warm. You should also look at short term and long term fuel trim.

Is the engine running unusually rich or lean? That would tell you something is amiss. Another basic check that should always be made is to check battery voltage and charging voltage. A low battery, weak alternator or over-voltage condition can all play havoc with onboard electronics.

Solenoids and relays all require minimum voltages to function properly, so if the battery or charging system are not within normal specifications you may have found the root cause of the problem.

If a problem has left no tracks no trouble codes or odd readings to steer you in a particular direction , is there a pattern? Does the engine only stall when it is cold or hot? Does it only occur during wet weather might be bad spark plug wires? A recent example of my own attempt to diagnose an intermittent condition occurred with my daughter's Saturn SC2.

The car had less than 40, miles on the odometer and was well-maintained thanks to me. The engine ran great, idled smoothly for a Saturn and passed the state emissions test. But every now and then, the engine would not restart after a short trip.

The engine would not stall, it just would not restart. It would crank normally but would not start until it sit for half an hour or so.

Then it would start and run fine. This happened maybe once every couple of weeks. I checked all the basics. The battery was at full voltage. The spark plugs were in good condition and properly gapped. The plug wires, coils and crank position sensor were all within specifications. Fuel pressure was within range. The sensor data on my scan tool all seemed to be normal and I could see no obvious problems that might prevent the engine from starting. Everything appeared to be normal.

To make matters worse, the car wouldn't act up for me. The starting problem would only occur when my daughter was driving the car -- and when she was at least 10 miles or more away from home. She'd call for help, and by the time I'd get there the engine would start right up and run fine. I quizzed her about her starting technique. Was she pumping the gas pedal? That's a no-no with fuel injected engines. Was the gear selector in park or neutral bad safety switch maybe? Was she doing anything unusual that might prevent the engine from starting?

After living with this problem for several months, it began to occur more frequently. Now the car was not starting every couple of days. We had lost all confidence in the car's reliability, so I loaned her my car to drive and started driving her car to see if it would misbehave for me.