why car struggles to start when engine is cold

Why Car Struggles To Start When Engine Is Cold

As temperatures drop, many car owners face the frustrating experience of turning the key only to be met with a sputtering engine that refuses to turn over. This difficulty starting the car when cold is an annoyance at best and a serious mechanical issue at worst.

In this comprehensive guide, we will explore the various causes of cold start problems, provide tips to avoid them, and outline potential solutions to get your car started and safely back on the road.

What Happens When a Cold Engine Struggles to Start

To understand why an engine may be hard to start when cold, it is important to first understand how a normal cold start functions.

In cold weather, engine oil thickens and does not flow as smoothly. Fuel also condenses more readily into droplets rather than vaporizing for the fuel injection system. In addition, metal engine parts contract which increases friction and resistance to motion.

To compensate, modern computer-controlled fuel injected engines increase idle speed, alter ignition timing, richen the air-fuel mixture, and take other steps to aid cold starting. However, if any part of this complex cold-start process suffers problems, the engine may struggle to turn over or catch at all.

Potential Causes of Hard Starting When Cold

There are a number of possible culprits that could be preventing your car from starting properly when cold:

Weak or Dying Battery

One of the most common reasons an engine struggles to turn over is a weak battery. In cold weather, a marginal battery has even more difficulty providing enough power to the starter motor.

Connections may be corroded or loose as well. Before condemning the battery, use a voltmeter to determine if the battery is providing at least 12.4 volts. Also check the battery cables and terminals for problems.

Weak Or Dying Battery
Weak or Dying Battery

Thick or Incorrect Viscosity Engine Oil

As mentioned above, oil thickens substantially at low temperatures. This increased viscosity makes it more difficult for the oil pump to push oil through the engine.

If using the incorrect weight oil recommended by the vehicle manufacturer, cold starts become even more difficult. The owner’s manual will indicate the proper viscosity for seasonal temperatures.

Faulty Coolant or Air Intake Temperature Sensors

These sensors relay temperature data to the engine computer. If the computer receives incorrect values due to faulty sensors, it cannot appropriately adjust cold start settings.

The engine may not get enough fuel and air to fire properly. Diagnostic trouble codes usually point to bad temp sensors.

Temperature Sensors
Temperature Sensors

Glow Plug Issues

Diesel engines rely on glow plugs to preheat the combustion chamber for an easier cold start. Weak glow plugs, failure to wait until they cycle properly, bad control module, or wiring problems can all lead to cold start woes. Follow proper glow plug testing procedures to identify issues.

Ignition Switch Problems

A faulty ignition switch can mimic a dead battery by failing to activate and provide power to start the car. Usually other electrical accessories will still work. Quick diagnosis is to listen for a starter click when the key is turned. No click indicates an ignition switch problem.

Starter Motor or Solenoid Failure

Starter motor failure is common in cold weather. Listen for odd grinding or whining noises. Intermittent operation where the starter works sometimes is also a sign.

The starter solenoid activates the motor when power is applied. It can wear out over time leading to no cranking. Testing the solenoid and motor electrically and mechanically will uncover faults.

Starter Motor Or Solenoid Failure
Starter Motor or Solenoid Failure

Fuel Problems

If fuel lines contain excessive moisture due to condensation in cold weather, it can freeze and cause fuel flow problems. Running out of gas, a plugged fuel filter,

or bad pump relay can also prevent enough fuel reaching the cylinders. It may only take a short squirt of starting fluid into the air intake to start the engine and indicate a fuel delivery issue.

Low Compression

While not necessarily tied to cold weather, an engine with worn piston rings, leaking head gasket, or valves that fail to seal will have difficulty starting year-round but cold starting exacerbates the problem. A compression test will reveal any cylinders with low compression. Engine repairs may be needed.

Ice Blocking Air Intake

It doesn’t take a severe cold snap to potentially ice over the air intake system. This blocks airflow and prevents a proper air/fuel mix in the cylinders.

Carefully check for ice formation around the air filter housing, throttle body, and intake piping. Gently remove any ice buildup before attempting to start the engine.

Ice Blocking Air Intake
Ice Blocking Air Intake

Tips for Preventing Cold Start Problems

While not every cold start issue can be avoided, there are preventative measures you can implement to help ensure your car fires up properly on cold mornings:

  • Use proper engine oil viscosity for seasonal temperatures. Fix minor oil leaks that allow oil to thin from fuel dilution.
  • Shelter your car or utilize block heater/oil pan heater. Fully charge battery and clean terminals before winter.
  • Check engine coolant antifreeze strength. Replace worn starter motor and solenoid.
  • Address pending engine repairs, especially compression issues. Check for TSBs related to hard cold starting on your vehicle.
  • Use fuel stabilizer to reduce moisture problems. Install battery warmer or change to AGM battery.

Ice Blocking Air Intake

If your initial attempts to start the cold engine fail, there are a few tips and tricks you can try before calling for a tow:

Ice Blocking Air Intake

Jump Starting – A jump from another vehicle or battery charger can provide extra current to turn over a weak battery. This may get you up and running temporarily.

Battery Warming – Warm a frozen or weak battery by wrapping in a blanket or applying a chemical warmer pack. You can also pour warm water over the battery.

Starting Fluid – While not recommended on fuel injected engines, a quick spray of ether into the air intake may help fire a stubborn engine. Use only as a last resort.

Idle Speed – If the engine catches but stalls, pumping the gas pedal may keep idle speed high enough to maintain operation until fully warmed up.

Electrical Load Reduction – Turn off all accessories like the radio, lights, heated seats, etc. to allow maximum current flow to the starter motor.

Patience – Modern engines cut fuel during cranking to prevent cylinder flooding. Pause 5-10 seconds between start attempts to allow systems to reset. Avoid holding the key at start for more than 10 seconds maximum.

Professional Diagnosis and Repair

If an engine continually fails to start in cold weather even after attempting basic remedies, further professional diagnosis is required. A technician can scan for trouble codes, assess battery/starter condition,

test sensors, and perform compression checks in order to isolate the root cause. From there, appropriate repairs can be made to provide reliable cold weather starting performance.

How to Open a Frozen Car Door

It’s a cold winter morning and you head out to your car, only to find the doors are frozen shut! Don’t panic, as there are several effective techniques you can use to open a frozen car door. With some patience and the right methods, you’ll be on your way in no time.

Ice Blocking Air Intake
Ice Blocking Air Intake

Assess the Situation

First, determine if only the door is frozen or if the entire door jamb/lock mechanism is encased in ice. If ice has built up around the door seals and into the lock components, this will require melting the ice carefully. Thawing only the door may allow it to pop open.

Use a De-Icer Spray

A de-icer fluid spray designed for door locks can quickly melt ice in and around the lock area. The fast-acting chemicals break down the ice so you can access the lock and open the door. Spray liberally into the door seam and keyhole. Most de-icers work in seconds.

Apply Heat Directly

If you don’t have a commercial de-icer available, you can use a high heat source directly on the frozen door components. A heat gun provides focused heat to melt the ice rapidly.

A hair dryer on high setting will work too. Hold the heat to the door handle area and around the side seams. Be careful not to damage any plastic or rubber parts.

Apply Heat Directly
Apply Heat Directly

Use Hand Warmers

For a more passive thawing option, place hand warmer packets along the door seals and locks. Activate several warmers according to package directions and place them strategically in areas needing to thaw.

The pouches slowly emit heat to melt the ice over 15-30 minutes. Replenish warmers as needed until ice is melted.

Pour Warm Water

In some situations, careful pouring of warm water may be effective. Heat some water on your stove or use the tap at its hottest setting. Slowly pour the water over

frozen lock components and along door seams. Caution: Control the water flow to avoid freezing again. Don’t pour water into door panel holes or you may damage internals.

Lubricate the Rubber Seals

Once ice is melted from the locks, frozen door seals likely still prevent opening the door. Apply alcohol-based products like hand sanitizer, rubbing alcohol or lock de-

icer spray to the rubber door seals. The alcohol helps detach the rubber from the door frame so the door can open. Reapply liberally until the door releases its seal.

Lubricate The Rubber Seals
Lubricate the Rubber Seals

Bump the Lock with Force

With the lock area thawed and lubricated, a decisive bump with force directly into the door lock area may provide just enough motion for the latch to release.

Do not strike glass portions of the door. Use your shoulder or rubber mallet to deliver controlled impact into the lock region. Repeat firmly if needed.

Prevent Re-Freezing

Once open, take steps to prevent immediate re-freezing. Insert the key and open/close the door multiple times to release any ice still inside the mechanism. Spray additional de-icer into the latch and wipe excess water away.

Consider covering the door seals with a towel or blanket temporarily. In extreme cases of ice blockage, the doors may need to be chipped open manually if other methods fail. Use extreme care not to damage the vehicle’s body panels or glass.

Preventing frozen doors in the first place is ideal by using preventive sprays and keeping door seals conditioned. With the right preparation and techniques, a frozen shut door doesn’t have to stop you this winter. Just stay calm and methodically melt away the ice until it opens up!


Why is my car struggling to start in the morning?

In cold weather, engine oil thickens making it harder for the starter to crank. The battery also loses power more quickly. Moisture in the fuel or ice blockages in intake passages can also prevent proper starting when cold overnight.

How do you fix a car that won’t start because of a cold?

Use thinner weight oil for winter, keep the tank full to prevent condensation, use fuel additives to absorb moisture, and install an engine block heater. Charging or replacing the old battery and checking the starter can also help with cold starts.

Can the cold make your car start weird?

Yes, cold temperatures change the behavior of engine fluids and parts. Oil thickens, the battery weakens, and metal components contract. This strains the starting system and alters fuel delivery, preventing smooth starts until the engine fully warms up.

What are the symptoms of a bad cold start sensor?

A failed coolant or air intake temperature sensor will cause issues like long cranking times before starting, stalling shortly after starting, rough idle, and the engine not responding properly to throttle input until fully warmed up.


Difficulty starting your vehicle when temperatures drop is frustrating but also preventable. Pay attention to warning signs preceding cold weather like hard starts when slightly cool. Maintain your car according to manufacturer recommendations

and address problems early before being stranded. Utilize the tips above to temporarily get your car running again if needed. For chronic or severe starting problems, seek professional technical help. With some diligence and care, your car’s cold start performance will keep you on the move all winter long.

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