Engine Stalling – Proper Troubleshooting and Maintenance

Engine Stalling - Check for Possible Causes
Engine Stalling - Check for Possible Causes

Engine stalling problems, can be hard to find and are often, sensor or temperature related.

Engine stalling is more likely to occur, during cold weather or when starting a cold engine.

So, this kind of engine stalling problem, often means the engine is not getting enough, fuel and/or too much air.

In addition, engine stalling problems, can be caused by almost anything, but are usually sensor related. Consequently, a cold engine, needs a fairly rich fuel mixture to start and to idle smoothly, while it warms up. So, what do you look for, when the car starts to shake and sputter, eventually causing engine stalling.

This can be a tricky problem to solve, because there are several things, that could be causing engine stalling. We’ve considered a few things that might be causing these problems, including, sensors and temperature. However, a faulty car engine, could be more serious.

Checking For Engine Stalling Problems - Possible Causes
Checking For Engine Stalling Problems – Possible Causes

So, finding the cause of the problem, takes experienced troubleshooting skills. Also, a working knowledge of your vehicle’s, air/fuel, and electrical systems. As a result, engine stalling issues of any kind, are always a challenge to diagnose.

Any Of The Following, Could Be Possible Causes Of, Engine Stalling Problems:

Engine Vacuum Leaks

The problems that arise, from an engine vacuum leak, can be more than annoying. Idle speed, that is way too fast, is one of the problems and stalling is another. Confirmation of an engine vacuum leak, can be a very loud hissing sound, coming from the engine area. Hesitation, can come from accelerator problems, but it also may be symptomatic, of an engine vacuum leak.

Locating Engine Vacuum Leaks
Locating Engine Vacuum Leaks

Check for loose or broken vacuum hoses, leaks around the intake manifold gasket or throttle body. As wall as, leaks around the (PCV) valve and (EGR) valve. A leak is a problem that creates both, poor fuel economy and a loss of power in the vehicle. The ultimate bad news is, damage to the engine itself.

A Bad (EGR) Valve

An (EGR) valve, that fails to close at idle, is another common cause of stalling. Most often, if the (EGR) valve is stuck open or can’t seat, because of carbon buildup under the valve.

Carbon Build Up On (EGR) Valve
Carbon Build Up On (EGR) Valve

As a result, it will allow too much exhaust, to be sucked back into the intake manifold. This can make the engine idle rough, misfire and/or stall. Inspecting and cleaning the (EGR) valve and the (EGR) port in the intake manifold, should cure the problem.

A Bad Mass Air Flow (MAF) Sensor

A faulty mass air flow (MAF) sensor, will cause problems, similar to low compression or low vacuum. Consequently, it will also show symptoms, similar to when your vehicle has low fuel pressure, from a faulty fuel pump.

Mass Air Flow (MAF) Sensor
Mass Air Flow (MAF) Sensor

Here are some of the most common symptoms, of a faulty mass air flow (MAF) sensor:

  • The engine is very hard to start or turn over.
  • Engine stalling, shortly after starting.
  • The engine hesitates or drags, while under load or idle.
  • Hesitation and jerking, during acceleration.
  • The engine hiccups.
  • Excessively, rich or lean idling.

A sensor that has been contaminated by fuel, varnish or dirt, will under report air flow. It will be slow to react, to changes in air flow as well. This can upset the air/fuel mixture causing, idle, stalling and hesitation problems. Cleaning the air flow sensor wire with aerosol electronics cleaner, can often restore normal operation and cure the problem.

Low Fuel Pressure

If the engine stalls, while idling or driving, the engine may be running out of fuel. This could be from, not enough fuel pressure, to keep it running. The most likely cause would be, a fuel pump that is not turning fast enough or is intermittently cutting out. If the vehicle is more than seven or eight years old, the fuel pump would certainly be suspect. But, as with the idle speed control circuit, don’t replace anything, until you’ve run some diagnostic tests.

Low Fuel Pressure
Low Fuel Pressure

The first thing to check, would be fuel pressure. Look up the specs for the year and model of the vehicle, then connect a gauge to the fuel system. Next, measure the pressure with the key on, engine off, then again with the engine idling. Fuel pressure, should be within specs, with key on, then drop 4 to 6 psi once the engine starts.

A Bad Idle Speed Control System

Idle speed on a fuel injected engine, is controlled by letting a small amount of air to bypass the throttle. The most common failure, is partial or complete jamming of the actuator (due to dirt, dust or even oil). The result is, that it cannot be smoothly controlled.

If the idle air bypass circuit, is clogged with dirt or fuel varnish, or the solenoid valve is sticking or broken, the engine may not get enough air to idle normally, causing it to stall. Replacing the solenoid valve, may then be the best course of action for this repair job.

However, cleaning the idle air bypass circuit in the throttle body, with aerosol throttle cleaner, will often remove the gunk. And, solve your stalling problem. If a good soaking with cleaner, fails to fix the stalling problem, check the wiring connector. It might be loose or corroded. If no wiring faults are found, you may have to replace, the idle speed control solenoid.

A Bad Engine Coolant Temperature (ECT) Sensor

If the coolant sensor is bad, and tells the (PCM) the engine is colder or warmer than it really is. Then, that can confuse the fuel mixture results. A faulty sensor (or sensor circuit) will often cause, cold driveability and emission problems. If the coolant sensor reads, colder than normal or cold all the time, the engine will run rich.

Engine Coolant Temperature (ECT) Sensor
Engine Coolant Temperature (ECT) Sensor

This won’t cause cold stalling, but it can make for a rough idle, once the engine warms up. If the coolant sensor reads warmer than normal, or reads hot all the time. Then, the (PCM) will lean out the fuel mixture too much, causing the engine to stall when it is cold.

A Bad Air Temperature (IAT) Sensor

This sensor, tells the (PCM) the temperature of the air, entering the intake manifold. The (IAT) sensor, can be damaged by backfiring of the engine. The sensor can also show, faulty readings, due to an accumulation of oil and carbon, wear and tear. Also, a poor connection after servicing the air filtering unit. The (PCM) needs, an accurate input, so it can balance the air/fuel mixture properly. Just like a bad coolant sensor, a bad air temperature sensor, can upset the fuel mixture, causing stalling problems.

A Bad Manifold Absolute Pressure (MAP) Sensor

The manifold pressure sensors function, is to provide, constant and instantaneous manifold pressure information, to the car’s computer. The computer uses the data, to calculate density and determine the engine’s, air mass flow rate. Consequently, this helps the computer determine, the amount of fuel needed, to create optimum combustion.

Manifold Absolute Pressure (MAP) Sensor
Manifold Absolute Pressure (MAP) Sensor

So, when a vehicle has a faulty manifold air pressure sensor, many different engine problems can occur. A faulty manifold pressure sensor has symptoms, that closely resemble, a vehicle with injector problems or low compression problems. If the (MAP) sensor, is not reading accurately, the (PCM) may add, too much fuel or not enough. This again, will cause engine stalling.

Low Engine Compression

So, there are many reasons why, low compression might exist in a engine. Sometimes, there will be low compression in just one cylinder of the engine, and other times, in all cylinders.

Engine Stalling
Low Engine Compression

Causes of low compression in engines:

  • Holes in Piston
  • Leaky Valves
  • Worn Timing Belt
  • Head Gasket Fails
  • Bad Piston Rings

Doing a compression test along with a cylinder leak down test, will confirm any issues.

Worn Or Fouled Spark Plugs

Ignition misfires, can make any engine stall at idle. When misfiring occurs, your engine will run slower than normal. So, a bad misfire, may cause it to stall.

Engine Stalling
Worn Or Fouled Spark Plugs

Symptoms could include:

  • Engine has a rough idle
  • Having trouble starting your car?
  • Your engine misfires
  • Engine surging
  • High fuel consumption
  • Lack of acceleration

So, a new set of spark plugs can restore a good hot spark. As a result, eliminating misfire and stalling problems.

Bad Or Poor Gas

So, bad gasoline in your tank, can cause stalling problems in a engine. Gas that does not contain enough dispersant-detergent additives, may result in deposits, building up and clogging the fuel injectors. Over time, fuel delivery becomes reduced or disrupted, causing the engine to run less smoothly, hesitate and even stall. Gas that does not have enough octane, has less resistance to detonation.

Engine Stalling
Bad Or Poor Gas

Combustion becomes less controlled and form shock waves, from simultaneous combustion events, cause knocking and pinging. Repeated impact from uncontrolled combustion, can damage the engine. Gas contaminated with water, other liquids and dirt, can cause a engine to misfire, sputter and stall. So, if the stalling started to occur, shortly after your last fill-up, suspect bad gas.


Idling issues can be very frustrating, but with some patient troubleshooting, you’ll have a real chance at figuring it out. Remember to always check your engine idle, with the air conditioning and defroster, turned off. Both of these systems, are designed to change the idle, when on, due to the demands on the engine. For some vehicles, this issue only happens in cold weather.

If that’s the case, then it is best to try and get it fixed, during the cold weather season. Again, there are many possible causes of this issue. So, it is important to start with the basics and rule out the simple things first. Then try working carefully, toward the more complicated causes of the problem.

Thank You !