Engine misfires are frustrating, but fortunately not a serious problem. It may seem a ‘mysterious’ issue to you (especially if you have limited knowledge about it) as it results in unpleasant sound and also creates minor issues in the engine.

A car engine misfire could be a temporary issue (in some cases) or continuous (if ignored/left untreated). In extreme cases, it generates engine trouble code.

Fortunately, the symptoms can be fixed easily and usually, it’s an inexpensive fix.

This article demystifies all the info related to Engine misfires. Let’s learn more about it. 

What is Engine Misfire?            

A car’s engine requires three elements for firing the cylinder – fuel, oxygen (for fuel burning), and sparkplug. Engine Misfire Damage is caused if there is a problem in any of these elements. 

Let’s understand the action in detail to have a clearer view of an engine misfire. 

All the actions of the combustion engine should be at the right time and in the right order to ignite the fuel and generate power.

When the piston moves an adequate amount of air-fuel enters the engine’s combustion chamber when the valves of the system open. As soon as the valves are closed and the piston moves upward the air-fuel blend is compressed. 

The spark plug then ignites this mixture with the power stroke and this elevates pressure-level in the cylinder. This high pressure forces the piston down very quickly and the crankshaft turns in the process.

The exhaust stroke opens the exhaust valves and removes the gases from the engine’s cylinder, and the same cycle keeps repeating. Issues in any of the components involved in the combustion process resulting in the engine misfiring.

Related Article: Symptoms of Bad Spark Plugs

Signs & Symptoms of Car Engine Misfire

#1 – Loss of Vibration, Power, and Stumbling

When the engine misfires there is a power loss in the vehicle. For this reason, the cylinders of the engine work less efficiently. Misfiring feels like intermittent stumbling, bucking, or jerking sourced from the car’s engine.

This condition results in slow or rough acceleration. One of the most common Engine Misfire Symptoms also includes a sense of vibration when the car is moving.

However, the severity of vibration is more when the vehicle is at idle.

#2 – Abnormal or Changed Engine Sound

The sound of the engine changes in the case of a misfire. You may also find abnormal sounds coming from the engines. A 4-cylinder engine generates sounds of a three-cylinder engine in cases when there is misfiring in one of the cylinders. Too strange sound from the car means it’s the sound of misfires.

#3 – Excess Fumes From the Exhaust

Pistons help in regulating fuel pressure in the car’s engine. Worn out/misplaced pistons lead to misfiring. As a result, the combustion cycle is disturbed and the engine’s exhaust generates more fumes than usual.

Related Article: White Smoke from Exhaust

#4 – Engine Stumbling When At Acceleration

You’ll face issues when accelerating the vehicle as there will be less power due to engine misfiring. You can feel massive or light jerks from your car’s engine.

Accelerating at high gears or high RPMs generates load on the engine in case there are misfires. So if there is rough acceleration or struggling engine then more likely they are signs of an engine misfire.

Read More: Reasons Car losing Power When Accelerating

#5 – Frozen Brake Caliper

If you sense your car jerking or feel like something is missing in the system when you slow down or start the vehicle possibilities are there could be an issue with the brake pads, the transmission downshifts or brake warped. All these conditions could have been caused due to the engine misfire.

Related Article: Symptoms of Bad Brake Caliper

Common Causes of Engine Misfire

#1 – Fault In The Ignition Parts

The ignition system includes parts like coil packs, spark plugs, and ignition wires corrode over time due to regular wear and tear. These parts have a limited lifespan and need replacement after a few years of car use. There comes a point when the engine’s spark plugs are unable to create sparks due to insufficient electricity supply.

It usually happens when one or more of these ignition parts start wearing out, there. Initially its intermittent misfires, but it worsens over time if left untreated.

#2 – Damage in Fuel System Component(s)

The next possible cause of the engine misfire is a faulty fuel system. If any part of the system wears out (even though if it is at a slow rate) there would be chances of misfiring due to clogging in the fuel filter, dirt accumulation in fuel injectors, or fuel pump/mass airflow sensor failure.

In such cases, the EGR valve doesn’t give passage to the exhaust wastage to reach intake manifold. Resultantly it creates misfiring in the engine.

#3 – Faulty Cylinder Walls

It’s one of the common reasons for car engine misfire. Cylinder walls damage causes misfiring engines which create sneezing or popping sounds. In certain cases, there is a strong burning smell usually a mix of steam, coolant, and gasoline.

The odor can be considered as a warning sign that indicates cylinder walls damage. It is best to contact a mechanic as soon as you discover the signs/causes of an engine misfire.

How Does Engine Control Unit Know When Misfire Occurs   

There ways by which a car’s engine control unit detects the misfire depends on the engine and model of the four-vehicle. The engine control module uses the in-built sensors for detecting the timing of spark plug ignition and fuel injection into the engine’s cylinder. It also helps in optimizing the mix of air and fuel. 

The crankshaft sensor of the engine control system helps in detecting a misfire. It measures the crankshaft’s position and conducts RPM calculation. The camshaft sensor is used by the crankshaft sensor for detecting the cylinders that are ready for ignition. The crankshaft’s speed increases a little when the gas pushes down the pistons on combustion stroke. 

When the crankshaft sensor fails to recognize speed increase, the engine control unit saves a DTC code on the misfiring cylinder. In cases where there is no ignition, the engine control modules use ignition coil resistance to measure the crankshaft’s position and detect misfiring issues through the system’s wirings.

Related Article: Bad Engine Control Unit

How to Diagnose Engine Misfire

Listed below are the top ways for diagnosing Engine Misfire

  1. Check the Spark Plugs

    Spark plug generates the spark needed to burn the mix of air and fuel to raise the cylinder pressure. Therefore, the spark’s accuracy is a thing of prime importance for the proper working of the system.

    In case of engine misfiring issue check whether or not the spark plug is loose. See if the sensors of the sparks plug are working properly.

  2. Observe the Ignition Timing

    Spark plug sensors are the next to check for diagnosing Engine Misfire. One of the popular causes of engine misfire is a fault in the ignition timing. Modern four-wheelers have advanced sensors to maintain timing.

    So if there is a fault in this part of the sensor system you can easily discover it using spark plug tester. At the same time, check the corroded terminals, carbon traces, rotor, and cap for cracks. Engine misfiring could be due to one of these reasons.

  3. Investigate the Ignition Coil

    Wearing off of the ignition coil is the next possible cause of misfiring. Even a single faulty coil can lead to multiple internal misfires. Check the DTC code P0200 if your car’s engine has a COP coil. Additionally, investigate the ignition control module in case there is misfiring in one or more cylinders of the engine.

  4. Examine the Fuel System

    If the fuel mixture is too thick or too thin then there are high chances of a misfire. Check the air-fuel mixture and make sure the two elements are in proper proportion. Plus, investigate the system for blockage in the fuel supply system. Low-quality chemicals and impurities damage the supply line of the fuel.

    Leakage in the fuel system will likely result in the improper air-fuel mixture. If left untreated it can also damage the engine’s fuel injectors. It is easy to diagnose the issue if the misfiring is caused due to issues in the fuel system.

    At the same time check the vacuum systems for leakage. If your four-wheeler misfires when it is moving at slow speed it is a clear indication of a fault in the vacuum system.

  5. Check the hose gasket

    Investigate the hose for loose connections or cracks. It can be easily checked using a bare finger. The hose needs to be changed if it’s too soft or too hard than usual. To check leakage – start your car’s engine and apply break if you hear a hissing sound there is likely a leakage in the gas hose pipe connection.

How to Fix Engine Misfire          

It takes around 30 minutes to fix the engine misfire. However, the approximate timing can be better determined by diagnosing the causes and symptoms of the car.

To fix the engine misfire at home first find the exact cause of the issue and then fix the issue accordingly.

Listed below are the solutions to fix the different engine misfiring problems

  1. When misfiring happens due to the high temperature of the engine get the cooling system repaired. 
  2. Replace or repair fuel pressure regulator if it is working at low pressure. Alternatively, you may take the help of a professional mechanic for the job. 
  3. Adjust the timing of the ignition system if it is set wrong.
  4. If the ignition system is causing misfiring then have the spark plugs, distributor cap, ignition wires, and rotor of your car checked and replaced ( if needed). 
  5. Check the engine control system of your vehicle and replace/repair the faulty components.
  6. If the partial/clogging of the car’s fuel filter is the cause of the problem then get it replaced with a new, high-quality one.
  7. Check the vacuum lines and replace them as required.
  8. Consider the replacement of the EGR valve if it is stuck open.
  9. If the drive axles are worn or loose get them replaced or repaired as needed.
  10. Replace or clean the fuel injectors in case there is dirt accumulation.

How to Prevent Engine Misfire         

Analyzing and solving the engine misfire problem can turn out to be a difficult and costly affair at times. Adequate time to time maintenance is the best solution to prevent the possible causes of an engine misfire.

It also helps in keeping the car in optimal condition and increases its life span. You may get the engine system components checked and replaced as required.

Can You Drive a Car with Engine Misfire?         

It is not dangerous to drive with an engine misfire. But, it’s best to avoid driving and get the issue fixed at the earliest. Ignore the issue will only worsen it over time.

In extreme cases misfiring causes damage to various components of the engine including the oxygen sensor and catalytic converter. Plus, driving with a misfiring engine is not good from a safety concern. The car may stop anytime due to loss of power.

Moreover, engine misfire reduces fuel efficiency and elevates the level of emissions.

How Much Does it Cost to Repair Engine Misfire   

Engine misfire repair is a nominal expense, but the average estimate of repair depends on the reasons for the misfire. The cost can be as little as $120 and it can go up to $1,000.

Like the average cost of a vacuum leak ranges from $200 to $700 (depending on the issue), bad fuel delivery costs $200 to $900, the average repair cost of the faulty ignition coil is $140 to $240.

Average cost of replacement/repair of broken piston rings – $1,400 to $2,500, bad spark plug wire- $100 to $200, fuel injector repair- $250 to $350, broken valve springs- $400 to $600.

Conclusion

Engine Misfire is a common issue. Though it’s not a serious issue, it can damage the car engine if left untreated for a long period. Misfire also causes loss of engine power which ultimately affects the vehicle’s performance.

You may issue like poor mileage, high fuel consumption, and more. Ensure a timely engine misfire diagnosis process for a smooth driving experience.