Diagnose Engine Stalling Problem

Engine Related Issues

By Rodney (Mechanics)

It can be annoying when we get the vehicle engine stalls very often. And for no apparent reason it can happen while you are driving. Temperature related is most thing causing the stalling problems, especially on cold weather it can happen often, it also can happen when the engine started on cold.

After Starting The Engine Stalls (Cold Quickly)

The engine had too much air and not enough getting fuel is common cause the engine stalling. To start the cold engine, it requires enough a rich fuel mixture and while the engine warms up it will idle smoothly when enough fuel supply. Below is the might caused the engine stalling problem occurs:

An idle speed control system faulty
By allowing a small amount of air to bypass the throttle, the idle/stationary speed at the fuel injection engine is controlled. The engine will stall when the engine may not get enough air to idle normally, this usually causing by the idle air bypass circuit is plugged with fuel varnish or dirt, broken or sticking the solenoid valve. To remove the stalling problem and remove the gunk use aerosol throttle cleaner to cleaning the idle air bypass circuit in the throttle body. Check the connector wiring when good soaking with cleaner not able to fix the stalling problem. It can be corroded or loose. The idle speed control solenoid should be replaced by the new one if you can’t find any wiring faulty.

A faulty or dirty airflow sensor.
Dirt or fuel varnish that contaminated a sensor will be slow to respond to fluctuations in airflow and also going to under report airflow. This may upset the fuel/air mix causing stalling, hesitation and idle issues. Fixing the sensor cable with electronics cleaner fix the issue and can restore normal operation. Use aerosol electronics cleaner to clean the airflow sensor wire can cure the problem and can restore normal operation.

An engine vacuum leak.
Check for leaks throughout the intake manifold body, vacuum pads, leaks around the EGR valve and PCV valve.

An air temperature detector faulty.
This sensors inform PCM about the temperature of the air that entering to the intake manifold. To get a properly balance the air/fuel mixture the PCM should have an accurate input. Just like another sensor, bad air temperature sensor could causing stalling problem on engine because it can disrupt the fuel mixture.

Fouled or worn spark plugs.
Engine stalling when idle can causing by ignition misfire. There less momentum to keep it going when the engine running slowly, engine stall because a bad misfire. Misfire for some case due for long time the spark plug never been replaced, it can be fix by replace the spark plug with the new one, this fix can eliminate the misfire issue and could restore a good hot spark. Another cause that make engine stalling is faulty crankshaft position sensor or weak ignition coil.

Coolant sensor faulty.
The fuel mixture can be screw up when PCM get an information from bad coolant sensor because it reads the engine is warmer or colder than it really is. The engine run rich when engine detected by the coolant sensor cold all the time or colder than normal. It can kills fuel economy, and when the engine warms up rough idle might be happen and won’t cause cold stalling. Engine can stalling when it is cold, because PCM lean out the fuel mixture over. It can happen when the coolant sensor detect and reads the engine hot all the time or warmer than normal. To fix this problem and to prevent engine stalling replacing defective coolant sensor is the solutions.

Bad gas.
Engine will stall if your gasoline is bad, no perfect burning when water or some other substance contaminated the gasoline or gasoline had more than 10% alcohol on it. After your last fill-up then the engine stall occur, it can be ascertained the problem is bad gasoline. To solve stalling issue because the bad gas, you should refill the tank from another filling station with the fresh gasoline and make sure to drain the tank before you refill it. In an emergency situation you can use gasoline that already filled (make sure on highway speed the engine runs OK) and try to find and stop on next filling station to refill the tank when it near empty.

Low engine compression.
If the engine has too much miles and due cylinders and/or piston rings are worn make the compression is low, or it has leaky valves (one or more), it may can’t keep the engine idling when not enough oomph. This is a problem or not depend on compression check reads result, if it’s a problem, the only fix is replace or overhaul the engine.

Bad MAP (Manifold Absolute Pressure) sensor.
Intake vacuum monitored MAP sensor, which the PCM (power-train control module) using it to determine the engine load. PCM will add less fuel or too much fuel if MAP do not reads accurately, this will causing stalling.

P0110 - Intake Air Temperature Sensor

Problem: On Idle And Stop On Traffic Light The Engine Started Stall.

When the engine isn’t fast enough (too low idle speed) it can caused the engine stalls (idle stall or stop light idle), or the alternator and/or the air conditioning compressor make engine being lugged down by a load on it. Another possibility engine run poorly due too much lean or too much rich of fuel mixture. And below is some causes the problem occur:

Unusually charging system overload.
When recharge the battery rundown alternator need working hard, engine will increase the load and idle rpm will be pulling down to the point that causes engine stalling. To see the battery is failing or battery is rundown, take a look on battery state of charge. Charge the battery if it low using battery charger or drive the car for half hour on the street. You need a new battery when battery is not holding a charge or it already failing.

A/C compressor is bad.
Overload refrigerant (over-charged) on A/C system or internal wear, lack of lubrication and the A/C compressor is binding up, when engine engaged it could be create the engine lugged down. If the issue is coming from the compressor, the problem will come out when A/C turn on.

NOTE: At idle good charging can produce 13.5-14.5 volts. Misfiring and stalling can caused by poor performance the fuel injectors and ignition system due low voltage input.

Problem: Engine Stalls While Driving.

Unexpectedly engine stalling while driving happen when engine losing spark (ignition-related). Ignition coil faulty (only have one coil on engine) or bad crankshaft position sensor is basic problem it happen. Engine can suddenly die for unknown reason because loses contact intermittently due the ignition switch faulty.

Check for the spark when this happen. Solve the issue by doing this, if engine has plug wires you need to pulling the plug wire off, crack the engine (ask for help from others) and put it on the end near the block. When engine crank and no snapping from plug wire or no spark seen, the problem is the ignition system.

WARNING: To prevent you get electric shock when the ignition system is working, DO NOT hold the wire.

If you see the spark on engine, the problem might be engine loss of fuel pressure. There no warning when fuel pump failed. If you can’t start the engine, time to towed the vehicle for repairs. Turn on the ignition and listen surroundings the tank for buzz. Fuel pump is not running when you don’t hear buzz (no buzz). It can be bad relay or blown fuse, however for old vehicle and have a lot miles on it the common issue is bad fuel pump.

Engine Stall - Service Engine Soon Warning
Engine Stall – Service Engine Soon Warning

Bad PCM relay is another possibility issue. Power supply often routed via one or two main power relays to the PCM. It’s just like pulling the plug on the PCM when relays loses contact momentarily. The PCM turns off and shut down the fuel injectors and the ignition, and it will causing engine stalling. To fix this, PCM power relay(s) need to be replaced or switched. If this way solve the problem, the issue is bad relay. If it doesn’t solve the problem could be PCM power circuit or PCM wiring fault.

Overcharging, low system voltage or loss of voltage is another possibility. To make other control modules and PCM operate correctly, it need a steady 12 volts. PCM will kill ignition circuit or the injectors temporary when supply voltage cuts out, surges about 16 volts or drop under 9 volts. That causes surge or drop in voltage can found somewhere in charging system or the electrical system. It’s not easy to find and need to use scan tool that can read and diagnosis the data when stalling happen. With scan tools output data hopefully the mechanic can found the issue and solve it by identify, isolate and then repair it.