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Home / Symptoms / Struggle To Start With Cold Engine

Hey, Why Does My Car Struggle To Start When Its Engine Is Cold?

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Four common causes for the vehicle struggling to start in the cold and related parts.
When the temperatures drop outside, everything on your engine seems to work twice as hard to get the vehicle started. Your vehicle's battery loses about half its capacity to crank over the engine. The oils that lubricate and complete certain functions of the engine flow at half the rate when it's cold, causing extra stress and pressure inside the engine. The gasoline burned during engine operation becomes harder to ignite as the temperatures drop outside. Ensure you have fresh oil and coolant and that your battery is up to the task.

Is Your Car Struggling To Start With a Cold Engine?

The engine struggles to start in the cold because of the battery. In this case, the chemical reactions within a battery are slower in the cold, whereas its internal resistance increases. Additionally, a weak fuel pump, dirty fuel injectors, heavier/thicker oil(common to occur in cold weather), and carbon deposits can also be culprits.

Many cars struggle to start when the cold weather hits, and it commonly doesn't mean a devastating issue. Pay attention to how the car behaves when you turn the key. Does it make a clicking sound, or is it completely silent? Every detail might rule out an issue with the car battery or something else, making the search quicker.

In this article, we will provide you with all the necessary information on communicating effectively with your mechanic about your car's issues when the temperature drops. Additionally, we will discuss specific issues that answer why the car won't start cold.

Let's Get To The Bottom Of It!

Is the engine barely cranking over during cold weather?

Your car's battery is a box that stores electricity. This electricity powers the car's parts, making the engine start. However, in cold weather, the battery struggles to perform because of a chemical reaction that happens inside. Imagine the battery is like a half-empty juice box. When it's freezing out, the battery acts like it's half of whatever it was in average weather. So if the battery is already weak, it might not have enough energy to help the engine start when it's cold.

Is the engine cranking for long before starting?

The fuel pump is a part of the gas tank. It ensures enough pressure to spray the gas into the engine so it can burn and power the car. But if the fuel pump is old and worn, it struggles to create enough pressure. This means the gas won't spray swiftly, and the engine won't burn properly, especially in cold weather. Also, as the pump ages, it takes longer to generate enough pressure to start the car. This is why sometimes you must turn the key for a long time before the car finally starts.

Is the engine starting and struggling to idle in cold weather?

The fuel injectors are like little sprayers that shoot gas into the engine. They make the gas into tiny droplets; this makes them burn quickly, helping the car go. But if the injector's nozzle gets dirty, the gas won't release in tiny droplets. Instead, it might dribble out and not burn properly, especially in cold weather, as gas doesn't ignite as easily in lower temperatures. So when the injector is dirty, and the weather is cold, the engine struggles to run smoothly, even when idling.

Does the engine only crank slowly if the outside temperature is below zero?

The oil in your car's engine is essential because it helps keep all the parts working smoothly. But it's not just any oil - it needs to be a specific oil that matches what your engine was built to use. The type of oil depends on the temperature where you live. If you use a thicker or heavier oil than your engine needs, it can cause damage to your engine. It's like trying to run a race wearing boots instead of sneakers - it's too heavy and slow. When it's cold outside, the thicker oil won't be able to move around the engine quickly enough, making it harder for the engine to start.

Is the "check engine" flashing on the dashboard and the car struggles to start in cold weather?

The spark plugs in your car help light a small fire inside the engine that makes it go. But spark plugs have a tough job because they must work in hot and harsh conditions. As you use your car, the spark plugs will wear out over time, and the gap will get bigger. This can make them weaker and not as hot, which can cause problems. When it's freezing outside, this problem gets even worse. If your spark plugs are already worn out, your engine might not be able to start at all, or it might run rough until the engine warms up.

When starting the engine in cold weather, is it immediately sputtering and dying in sequence?

The engine in your car needs air to work correctly, and the air comes in through the intake. But over time, some dirty stuff called carbon deposits can build up inside the intake because of the way the engine works and because of heat. When there's too much carbon buildup, the airflow through the intake can be blocked. This can cause the engine to get too much fuel and not enough air, making it run poorly or not start at all, especially when it's freezing outside.

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Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Weak fuel pump

The proof image provided shows the actual fuel pressure reading, which confirms that the low fuel pressure is causing the extended crank time when the car is cold.

A customer dropped off their vehicle and complained it started very slowly in cold weather. The technician took the car for a test drive and noticed that the engine had an extended crank time before starting, and also saw that the check engine light was on.

During a vehicle health inspection, the technician scanned the car's computer for trouble codes and found P0171 and P0174. These codes indicate a system lean condition in bank 1 and bank 2 of the engine. As a result, the technician requested additional authorization for diagnostic testing.

After receiving authorization, the technician used a specialized scanner to check the fuel trims and found they were within the normal range at idle. However, due to the trouble codes and symptoms reported by the customer, the technician decided to test the fuel pressure.

Using a mechanical fuel gauge attached to the fuel rail, the technician found that the fuel pressure was only 37 PSI, while the manufacturer's specifications recommend 58 PSI. This means the fuel pump is failing and must be replaced.

Heavy oil

The proof image is of the proper oil viscosity for the engine on the oil cap.

A customer dropped off their car at the shop and complained it cranked slowly after an oil change during a road trip. The customer attempted to jump-start the vehicle, but it still cranked slowly.

During the test drive, the technician did not notice anything wrong with the car. However, the technician experienced a slow cranking issue the following morning.

The technician checked the starting and charging system, and everything tested okay. Then, the technician suggested leaving the car outside overnight to try it in the cold morning to find out the root cause of the problem. So the following morning, the technician started the vehicle, and it cranked slowly.

To find the cause of the problem, the technician performed a voltage drop test on the positive and negative battery cables to ensure the voltage was going to the starter. While investigating, the technician discovered that the oil change sticker on the vehicle's window showed that 15w40 oil had been used instead of the manufacturer-specified 0w30 weight oil.

The technician then called the number on the oil change sticker and learned that the customer had gone to a diesel shop that stocked only the 15w40 oil, which is not recommended for their vehicle.

This means that the 15w40 oil represents a heavier mixture, which is too dense for lighter vehicles. So instead, the technician recommended an oil service using the manufacturer-specified oil weight to solve the slow cranking problem.

Carbon deposit

The proof image shows that the carbon buildup on the throttle plate is causing the car to have trouble starting on cold days and perform poorly overall.

A customer dropped off their vehicle because it had been getting worse gas mileage lately; they also mentioned it was having trouble starting in cold weather. The car would start, but then it would sputter and die several times before finally staying on.

During the technician's test drive, they noticed that the car's response when pressing the gas pedal was not very good. They also noticed that the engine's idle was inconsistent, with the RPM gauge fluctuating.

During the vehicle health inspection, the technician found nothing to explain the customer's concern. However, they were authorized to perform additional diagnostics.

The technician used a specialized scanner to check for trouble codes but found none. They then examined the live data on the vehicle and discovered that the calculated load at idle was unusually high at 33%.

When the technician took the car for a drive and pushed the gas pedal down at around 40 mph, the calculated load rose to 92%, indicating that the mass airflow sensor was working correctly.

Upon gaining access to the throttle plate and intake, the technician noticed they were caked with carbon buildup. Therefore, they recommend an upper air intake fuel service and cleaning to remove the buildup. After performing the service, the calculated load at idle dropped to 22%.

Dirty fuel injectors cause the engine to receive unproper fuel amounts, leading to bad combustion and vibrations while also making the car struggle to start

The proof image shows a dirty close-up of a removed injector tip, which could cause the car to struggle when starting on cold days. However, the technician believes cleaning the injectors will fix the issue and improve the car's fuel economy.

A customer brought their car in because it struggled to run when starting in cold mornings. They also mentioned that the car's fuel economy had been getting worse, and the engine would shake sometimes mid-drive. The technician took the car for a test drive but didn't notice anything unusual. Then, however, they saw the check engine light on.

During the vehicle health inspection, the technician did a code scan and found two codes that suggested a lean fuel mixture. In addition, the fuel trims at idle were within an acceptable range, but this indicated there could be a mechanical or fuel-related issue.

To investigate further, the technician attached a vacuum gauge to the manifold and a mechanical fuel pressure gauge. Both of these tests were normal.

The technician then went on a test drive with an assistant to monitor the oxygen sensors and fuel trims. They found the oxygen sensors were running low, and the fuel trim dropped as they drove. Based on this information and the customer's complaint, the technician suspected the fuel injectors were clogged and dirty.

Finally, they recommended a GDI fuel service and retesting to fix the issue. A GDI fuel service, or Gasoline Direct Injection fuel service, is a type of automotive maintenance that involves cleaning a car's fuel system.

Faulty battery resulting in electrical issues and preventing the car from starting in cold weather

The proof image shows the battery testing. Unfortunately, the battery was not providing enough power to start the car, even though it was rated for much more.

A customer brought their car and explained they had trouble starting it in cold weather. They mentioned that the engine barely cranked over, and the car wouldn't start. Later in the day, the car started when it was warmer but still cranked slowly. Also, the headlights were dimmer in general.

During the test drive, the technician noticed that the car started but cranked slowly. The technician then did a vehicle health inspection and tested the battery using an electronic tester. The results showed that the battery had 232 CCA, much lower than the battery's rating of 700 cold-cranking amps.

Note that CCA stands for "Cold Cranking Amps." It measures the battery's ability to start the engine in cold temperatures. The higher the CCA rating, the more influential the battery is at starting the engine in cold temperatures.

The technician also tested the charging system and found it working correctly. However, based on the tests, the technician determined the battery was faulty and needed to be replaced. The battery no longer provided enough power to start the car properly, especially in cold temperatures.

Worn spark plugs

The proof image shows the gap between a worn spark plug and a new one. This was causing the car engine to misfire during cold starts in this case.

A customer dropped off their vehicle and reported trouble starting in cold weather. Plus, they mentioned that the check engine light came on while driving two days ago; the light stayed on permanently after flashing a few times.

During a test drive, the technician noticed the check engine light was on and that the car hesitated when accelerating. However, during a vehicle health inspection, the technician found nothing related to the customer's concern.

The technician then used a vehicle code scanner and found the car had a problem with all four cylinders misfiring. This meant fuel was not burning correctly in the engine, causing power loss and increased emissions. The technician then asked for authorization for additional diagnostics and used a dedicated scanner to verify the codes.

The technician started the car and monitored the misfires using the scanner. Under load, all four cylinders were misfiring randomly. The technician then checked the spark plugs and found a gap twice as wide as the manufacturer's specification.

This meant the spark plugs were not creating the right spark to ignite fuel in the cylinders. As a result, the technician recommended replacing all four spark plugs with new ones.

In addition, the technician suggested performing a fuel service to clean the injectors and remove any carbon deposits. This was because dirty injectors could render uneven fuel to the engine, causing misfires. Carbon deposits can also accumulate over time and reduce engine performance.

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

Vehicle Symptoms

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Typical Fixes Pages