Car Stalls At Low Speeds (Why It Happens And What To Do)
Does your car have a tendency to stall on you at low speeds? Have you tried all possible fixes and suggestions from your friends and on the web but nothing seems to work? If that’s you, you’ll find this guide helpful.
Your car stalls at low speeds due to a faulty idle air control valve. Replacing this valve with a new one is pretty cheap and can help solve the problem. Other possible causes include a dirty throttle body, fuel system issues, bad mass airflow sensor, or worn-out spark plugs.
Read the following guide to discover full details about why your car stalls at low speeds and what you should do about it, plus other helpful info and tips relating to this issue.
What causes your car to stall when driving at low speeds?
Generally, your car stalling at low speeds or right after starting usually indicates you’ve got a problem with the air-to-fuel ratio. This is unlike stalling at high speeds which usually occurs due to charging system and ignition issues.
The issue of your engine stalling at low speeds or low RPMs isn’t uncommon. We’ve come across many other car owners complaining about the same issue, where their cars’ RPM goes all the way to 0 and their engines shut off.
In most of the cases we analyzed, this issue usually only happens when you’re driving at low speeds, say when braking, accelerating from a stop or driving in stop/go traffic.
We found that there’s no single cause for this issue. It arises from a variety of issues running from a faulty IAC valve to a dirty throttle body, fouled spark plugs, and so on.
Below we discuss all the major causes for your car stalls at low speeds problem:
Dirty or faulty idle air control valve
The most common reason why your engine stalls at low speeds is a faulty idle air control valve (IACV).
This valve is responsible for controlling airflow around the throttle plate. If this component becomes dirty or faulty, it keeps the engine from getting the air it needs, causing it to die.
Also, when your car is under load, it’s the job of this valve to compensate by raising the engine RPMs.
If your engine cuts off, then you may have a tired or faulty IAC valve which causes your engine to stall before the ECU gets to correct the load.
Throttle body issues
A mechanical throttle body that’s dirty or restricted easily limits the flow of air, causing your engine to stall at low RPMs.
Car models from the mid-2000s usually come equipped with electronic throttle bodies which are controlled by the car computer.
If this component or its circuitry has any faults, it can also make the engine stall.
Sensor issues
Faulty sensors can also make your engine stall at low speeds. For cars that use speed density fuel delivery system model, the vehicle computer controls their fuel injector performance based on the input it gets from these sensors:
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor (TPS)
- Intake air temperature sensor (IAT)
- Coolant temperature sensor (CTS)
If any of these sensors and their related wiring develops faults, they can cause stalling.
For cars that use mass airflow fuel delivery systems, they control fuel injector performance based on the input they get from the mass airflow (MAF) sensor. Thus, if the MAF sensor and its related wiring fail, your engine may stall.
The good news is that faulty sensors usually trigger a check engine light. This means there’s a diagnostic trouble code in your car computer that you just need to pull with a scanner to give you clues on how to repair the problem.
Vacuum leaks
Vacuum leaks are also notorious for causing your engine to stall at low speeds. When your engine system suffers vacuum leaks, it permits unwanted air to get into the engine. As a result, your engine runs lean (i.e., it gets less fuel and too much air).
If the leak is too large, then it will make your engine stall. Note that common sources of vacuum leaks in your engine include lines and hoses, intake manifold, and positive crankcase ventilation.
Fuel delivery problems
If your engine suffers low fuel pressure, it may also result in the engine dying. Poor fuel pressure can be caused by various fuel delivery components. One such component is the fuel pump.
If the pump is weak or defective, it will starve your engine off the fuel, causing it to stall. Clogged fuel filter or fuel line can also affect the fuel pressure and make your engine stall.
A malfunctioning fuel pressure regulator is another likely culprit. A clogged fuel injector will not directly make your engine stall but will cause misfires.
Worn-out spark plugs
Spark plugs are a crucial part of your car’s ignition system. So, if they get worn out, are not properly installed, or are simply out of spec, they can make your engine misfire and lose power.
Worn-out or dirty plugs can’t fire properly, and thus can’t ignite fuel in piston cylinders in time—resulting in engine misfires.
Other possible causes for car stalls at low speed include:
- Car computer issues: Your engine computer, or the engine control module/unit, helps monitor and regulate all the areas of your engine performance. If this unit or its circuitry develops any issues, then it may also cause your engine to stall.
- Engine problems: If your engine has low compression power, it won’t produce sufficient power to continue running. This may cause it to stall after being started or when loaded.
What to do if your car stalls at low speeds?
Now that we have discussed what makes your car stall at low speeds, the next thing you need to do is decide which of these issues is affecting your car.
You need to have diagnostics carried out on your car to prove the reason the engine cuts off at low speeds. Just having the above list of possible causes won’t help you until your vehicle gets checked by an expert.
That said, we have shared some tips on how to fix the stalling issue in your car.
You’d want to start by removing the throttle body and giving it some cleaning. If you have an electronic throttle body, its circuitry should be inspected.
If it looks all good but you still have the stalling issue, then you should get a new throttle body/actuator.
Another fix is to remove the IAC valve and give it cleaning as well. In most car models, the IACV is housed within the throttle body.
Get a professional mechanic to locate the vacuum leak source as well and repair it if necessary. In case of leaks, you may be required to replace Positive Crankcase Ventilation (PCV) valve and hoses.
Sensor-related issues usually trigger a check engine light, so you’d bet better off scanning your car computer for fault codes and looking them up on Google to find out what sensor is faulty.
Regarding fuel delivery system issues, we advise you to let a professional inspect it for you. This is due to the high risks tied to gasoline. If it turns out your car has low fuel pressure, then the mechanic will recommend fuel pump replacement.
As you can, some of these repairs are a bit complicated for an average car owner to handle. Therefore, we recommend getting a good mechanic to help you with the repairs.
What causes intermittent stalling at low speeds?
If you have a problem with your car stalling intermittently at low speeds, you’re probably wondering why this is happening and what fixes you should try to fix it.
The issue could be due to fuel delivery system problems, vacuum leaks, dirty air filter, faulty IAC valve, ignition system failing, and a dirty throttle body.
If the check engine light comes on during these intermittent stalling instances, then your car may be having sensor problems.
Some simple fixes you should consider to see if they help with this issue include getting a new fuel filter, cleaning the IAC valve, cleaning the throttle body, cleaning the MAF sensor, replacing the throttle position sensor, and so on.
If these fixes don’t solve the problem, you can get a mechanic to inspect your car vacuum leaks as they could be another culprit. In this case, you may need to replace the clogged PVC valve to solve the leaky situation.
Your best bet is to get a qualified auto mechanic to diagnose your car and find out exactly what is causing the intermittent stalling.
The mechanic will present you with the culprit and what needs to be replaced/repaired to fix the problem.
Why your car stalls when turning sharply at low speed
The first step to diagnose a car that stalls when turning sharply at low speed is to get error codes pulled from the car computer.
This will help point you in the direction when diagnosing your car.
You may find that the problem is caused by sensor problems such as idle, MAF, MAP sensors, and so on.
The stalling could also be due to a bad IAC valve which just needs some cleaning. Or in some cases, you’ll need to be replaced it.
You may also try replacing the Throttle Position Sensor (TPS) to fix this stalling issue. Also, clean the throttle body as the carbon buildup on this component may be causing the stalling problem.
Cleaning the injectors by adding some injector cleaning solution in your gas and see if it helps solve the problem.
Vacuum leaks are another potential culprit, so be sure to inspect your hoses for damages and replace any bad PVC and hoses.
Above all, be sure to inspect the condition of your spark plugs and their wiring and fix them as necessary.
What makes your car stall occasionally at low speeds but no error codes?
If your car stalls at low speeds, it can be a head-scratcher trying to prove what’s causing the stalling. Nonetheless, the culprit can still be uncovered if you get a good mechanic to inspect your car.
As we discussed earlier, the most common culprits for car stalling at low RPMs revolve around faulty idle air control valve, throttle body problems, fuel delivery issues, sensor issues, vacuum leaks, or even ignition-related problems.
Get an experienced mechanic to diagnose your car and find the root cause of this stalling problem and then recommend the best fixes to end the stalling issue.
Car stalling can happen at any time and can be a major safety concern, especially when it happens at idle or at stops. At MotorAdvices, we have articles that address a range of issues related to car stalling, including how to deal with stalling at idle and at stops. Our article on car stalling at idle explains the common causes of this problem and provides tips on how to troubleshoot it. Additionally, our article on car stalling at stops discusses the possible reasons for stalling when you come to a stop and suggests ways to prevent this issue. Visit MotorAdvices to learn more about how to keep your car running smoothly and avoid stalling, no matter when it happens.Related Questions:
In most cases, stalling doesn’t hurt your engine. It may also cause a little wear on some of your engine components which is insignificant and nothing to worry about. However, it’s still a good idea to get to figure out what your car stalls as soon as possible to avoid risking your life and that of other road users.
The most common sensors known for causing engine stalling include the mass airflow sensor, throttle position sensor, and engine coolant temperature sensor.
If your engine stalls while in traffic, stay calm and don’t panic! First, you ought to understand that your stalled car has lost all its braking power and power steering, so you must complete the functions through manual force.
- Step 1. Apply the brakes at a steady but reasonable rate, then look for a safe place to pull over.
- Step 2. After checking that it’s safe to pull over proceed to do it while using your car’s turn signal.
- Step 3. Once out of the way, put your car in neutral (for manual) or park (for automatic) and then set the emergency brake.
- Step 4. You can then go ahead and get a wrecker to tow your car to the nearest auto repair shop for inspection and repairs.
Final Word
In most cases, your car stalling at low speeds happens due to fuel flow obstruction or simply an issue with the air-fuel ratio. The most common causes for this issue include a failing mass airflow sensor, dirty throttle body that needs cleanup, faulty idle air control valve, vacuum leaks, fuel delivery system issues, or worn-out spark plugs.
You can diagnose your car to find out what is causing the problem using the diagnosis tips we have shared in the above guide. Scanning for the error codes will help make your diagnosis even easier. After identifying the problem, you should get a professional mechanic to complete the inspection and make the necessary repairs to fix your car-stalls-at-low-speeds problem.
