It can be an unnerving experience when your car suddenly dies while driving down the road, but then restarts again like nothing happened. This intermittent problem is likely due to an underlying issue that needs diagnosis and repair. In this article, we’ll explore the most common reasons a car turns off while driving but turns back on, and what you can do about it.
Main Causes of Car Dying While Driving
There are a few key systems in your car that could be the culprit for causing it to stall while driving but start back up again:
- Fuel system – Issues with fuel pressure, the fuel pump, or clogged fuel filters can cause the engine to die while driving due to lack of fuel.
- Electrical system – Faulty wiring, a deteriorating battery, or bad alternator can cause electrical issues that lead to sudden engine shut off while driving.
- Ignition system – Malfunctioning components like spark plugs, coils, crankshaft sensors can cause misfires and engine dies.
- Engine Sensors – Defective sensors such as camshaft sensors and mass airflow sensors can provide incorrect input to the car’s computer and lead to stalling.
- Overheating issues – A car that is overheating can die while driving and leave you stranded until it cools down enough to start again.
Let’s explore these common causes in more detail:
Fuel System Problems
One of the most common causes for a car dying while driving but being able to restart is a fuel system problem. Here are some specific issues to look out for:
- Faulty fuel pump – The fuel pump is responsible for delivering fuel from the gas tank to the engine. A failing fuel pump can cause low fuel pressure that leads to stalling while driving. Warning signs include whining sounds from the rear of the car where the fuel tank is located.
- Clogged fuel filter – Debris accumulation in the fuel filter restricts fuel flow to the engine. This starving of fuel can manifest as sudden engine shut off while driving. Replacing the fuel filter regularly can prevent this.
- Faulty fuel pressure regulator – This component maintains the proper air-fuel ratio (AFR) by regulating fuel pressure. A bad regulator can cause too much or too little fuel to reach the engine, causing it to die while driving.
If you suspect a fuel system problem, check your fuel pressure at the fuel rail. Pressure should be around 30-40 psi when the engine is off, and 50-60 psi when running. Consistently low or high readings indicate a problem.
Electrical System Issues
Electrical system problems are another common culprit for cars dying intermittently while driving:
- Bad battery – If the car battery is old, it may not be able to deliver enough power to start the engine. Warning signs are dim headlights, interior lights, and difficulty starting. Have the battery tested at an auto parts store.
- Failing alternator – The alternator charges the battery while driving. If it’s malfunctioning, the battery may lose charge leading to engine stalling. Warning signs are battery light coming on while driving just before the car dies.
- Faulty wiring harness – Damaged or deteriorated wiring and connectors can cause electrical shorts. This leads to stalling, no starts, or the engine turning off while driving. Check for damaged wires in the engine bay and under the dash.
- Corroded battery terminals – Corrosion on the battery posts prevents proper contact. Clean terminals thoroughly and reconnect securely. Apply a terminal protector afterwards to prevent further corrosion.
Ignition System Problems
Components involved in igniting the fuel-air mixture are also common culprits:
- Faulty crankshaft position sensor – This sensor monitors crankshaft speed and position to control ignition timing. If it fails, it leads to engine misfires and causes the car to die. Code P0335 usually indicates a bad crank sensor.
- Bad camshaft position sensor – This sensor determines the open/close timing of engine valves for fuel intake and exhaust. Defective sensors throw off valve timing causing stalling. Code P0340 usually indicates a faulty camshaft sensor.
- Failed ignition coils – Ignition coils deliver spark to the spark plugs to ignite the fuel mixture. When they fail, the engine loses spark resulting in stalling while driving. Codes P0301-P0308 indicate which cylinder has a bad coil.
- Old spark plugs – Over time spark plugs wear out, inhibiting them from producing a spark hot enough for proper combustion. This results in a misfire causing the engine to die. Inspect and replace spark plugs per the maintenance schedule.
If the car’s check engine light comes on and it stalls while driving, overheating is a likely cause. Here’s why it happens:
- Low coolant – A coolant system leak or previously overheated engine can lead to low coolant. This reduces the engine’s ability to cool itself while driving leading to overheating and stalling.
- Faulty radiator – The radiator cools the heated coolant coming from the engine. If the radiator is clogged or damaged, it cannot dissipate heat efficiently. This leads to overheating and engine dying.
- Broken serpentine belt – This belt drives the water pump to circulate coolant. If broken, coolant flow stops, causing the engine to overheat and die while driving.
- Bad radiator fan – The radiator cooling fan turns on when the engine gets hot to accelerate cooling. A faulty fan leads to overheating and causes the engine to turn off while driving.
- Thermostat stuck closed – The thermostat regulates coolant flow to control operating temperature. When stuck closed, it prevents coolant from circulating leading to overheating and stalling.
If your car is overheating, pull over immediately to prevent severe engine damage. Have the cooling system inspected as soon as possible.
Steps to Diagnose the Problem
When your car turns off while driving but restarts later, follow these diagnosis steps:
- Scan for diagnostic trouble codes (DTCs) – Use an OBD2 scanner to pull any codes. They indicate which sensors or components are faulty. Common DTCs for stalling are P0300, P0301, P0351, and P0501.
- Do visual inspection of engine bay – Look for any loose wiring, damaged hoses, or leaks. Also check serpentine belt condition.
- Perform voltage drop tests – Use a multimeter to check for excessive voltage drops indicating bad wiring or connections. Measure key circuits like power and grounds as well as sensor connectors.
- Conduct fuel pressure test – Determine if fuel pressure is in spec when engine is off and running. Low pressure indicates a faulty fuel pump or clogged filter. High pressure points to a failed regulator.
- Check for spark – Use a spark tester to confirm all cylinders have good spark when cranking the engine. No spark means an ignition system problem.
- Perform compression test – This determines if cylinder combustion chambers have good compression. Low compression reduces engine power and causes stalling.
- Check engine fluids – Make sure coolant, brake fluid, power steering fluid, and oil are at proper levels. Top up any low fluids.
Following these diagnostics will help isolate the root cause of your car dying but restarting so you can get it fixed properly.
Based on the diagnostics, here are some common solutions for a car that stalls while driving:
- For fuel system problems – Replace the fuel filter, fuel pump, or pressure regulator as needed. Use fuel injector cleaner to restore injector performance.
- For electrical system issues – Recharge the battery, replace battery terminals, check alternator belt tension, and fix any damaged wiring.
- For ignition problems – Replace worn spark plugs and coils. Swap out crankshaft and camshaft position sensors.
- For overheating – Top up coolant, flush radiator, replace thermostat, fix leaks, and check cooling fans.
- For sensor problems – Replace any defective sensors like camshaft sensor, mass air flow sensor, manifold absolute pressure sensor.
- For computer problems – The engine computer may need software updating or replacement if diagnostics are all normal.
- For misfires – Besides ignition parts, misfires can be due to intake leaks, bad fuel injectors, or valves out of adjustment.
Properly diagnosing the specific cause is key before attempting repairs. Simply replacing parts without determining root cause often fails to permanently fix cars stalling while driving.
Preventing Future Stalling Issues
Once you’ve resolved the underlying problem, here are some tips to help prevent future instances of your car dying while driving:
- Perform regular maintenance like oil changes, fluid checks, battery testing as recommended in owner’s manual. Replace worn parts early.
- Inspect all belts, hoses, seals, clamps for deterioration. Replace as needed. Tighten loose clamps.
- Clean battery posts and cable connections to remove corrosion and ensure solid contact.
- Use quality gasoline and keep tank over 1/4 full to avoid fuel pump issues.
- Address pending error codes or check engine lights to prevent bigger problems down the road.
- Consider installing an aftermarket fuel pump if you have an older vehicle prone to weak pumps.
- Have alternator output tested if over 5 years old. Replace early to avoid on-road failures.
- Install an engine oil catch can to prevent oil deposits in intake system that can cause misfires.
Driving a well-maintained car is your best defense against the annoying and potentially dangerous problem of stalling while driving. Addressing problems promptly also helps avoid more costly repairs down the road.
When to Call a Mechanic
Intermittent issues like a car dying while driving can be tricky to resolve yourself. If you’ve done thorough diagnostics and are still stumped, it’s best to seek professional help.
Seeking an experienced mechanic is recommended in these cases:
- You lack the tools, skills or time to properly diagnose the problem.
- The issue seems electrical and could involve extensive wiring harness testing.
- The problem is complex like an intermittent misfire without any codes set.
- The car stalls randomly with no discernible pattern making it hard to reproduce.
- You’ve replaced several parts and the issue still persists.
- The stalling causes safety concerns due to where it occurs like at intersections.
- You need help accessing or interpreting scanner diagnostics data.
- Further testing like cylinder leakdown or crankshaft variation learn procedure is required.
- Internal engine damage may have occurred requiring removal to inspect and repair.
Finding a knowledgeable mechanic you trust is invaluable when dealing with complicated or hard to diagnose stalling problems. It saves you time, money, and frustration in the long run.
Having your car stall randomly while driving can be both annoying and dangerous. By understanding the most common underlying causes and methodically diagnosing the problem, you can get your car running smoothly again. The key takeways are:
- Fuel, ignition, electrical and sensors are common culprits for stalling issues.
- Thoroughly check the fuel and electrical systems before replacing sensors or computer parts.
- Do visual inspections and tests like fuel pressure, voltage drop, spark, and compression checks to aid diagnosis.
- Fix any underlying issues like worn parts, leaks, damaged wiring before the problem escalates.
- Well maintained cars are less prone to stalling problems down the road.
- Seek professional help for intermittent or complex stalling issues you can’t resolve.
With diligent troubleshooting and repairs, you can get your car running reliably and prevent those terrifying instances of your engine cutting out without warning. Drive safely!