Why Is My Diesel Car Misfiring?

The chemical reactions required for combustion are hampered when there is a lack of air in the engine.

How to Diagnose Engine Misfires and Tips For Fixing the Problem:

Randy in Alabama has a question: What are some possible causes of diesel engine misfiring, and how do you remedy it?

Engine misfires are prevalent in diesel engines, but the good news is that they are usually a simple problem to diagnose.

Misfires in automobiles are a completely different beast than misfires in diesel engines. Diesel engines use compression to ignite the fuel, whereas gasoline engines use a spark from an ignition system. When it comes to automobile misfires, the ignition system is the first place to look. Inspection of the ignition wires, spark plugs, distributor cap/rotor components, and ignition coil are the next steps in diagnosing the problem. Because the components stated above wear down over time, the spark generated for ignition is frequently not correctly transported. The engine will not be able to turn over if the air/fuel mixture in the combustion chambers cannot be ignited.

1. Make certain you’re using high-quality diesel fuel. Examine the diesel fuel to ensure it is free of pollutants such as water, dirt, or oil.

2. Examine the service log for the fuel system. Replace the fuel filters as needed, and use a fuel water separator to drain water from the system.

3. After you’ve double-checked that the engine is in good working order and that the fuel filters have been replaced, look for any broken or leaking high-pressure fuel lines. Although you may pressure test the fuel line, most leaks are visible and easy to locate.

4. Check for low fuel supply pressure in the fourth step.

5. Inspect the gasoline line and transfer pump for bends or kinks.

6. Inspect the gasoline tank for a clogged suction pipe or a plugged suction hole.

7. Inspect the fuel system for air and fuel pressure.

8. Replace the fuel filters if the pressure is less than what is specified.

9. Check for a free-moving poppet in the return valve; if it is low, replace the transfer pump.

10. If none of the foregoing diagnoses the problem, there are four further possible causes of engine misfire:

The good news is that engine misfires are rather common and are not indicative of a more significant problem with the diesel engine. Each engine is unique, and Mack E-7 or E-Tech engines, for example, have a thicker fuel line than a Detroit Series 60 or a CAT 3406E. The problem with a Mack engine could be with the injectors rather than the fuel line. It’s critical to inspect each engine component individually to rule out problems one by one. Begin with the simplest problem and work your way up. If your engine continues to misfire, please contact a diesel parts specialist for assistance.

How do you diagnose a diesel misfire?

Rough running, a decrease of power and fuel economy, and the unwanted check-engine light flashing on the instrument panel are all common signs. Many system faults can be the cause, but let’s look at the three most common sorts of misfires.

What does a diesel misfire sound like?

So, how do you describe a misfire? The engine will emit a sudden sound that can be described as popping, sneezing, or backfiring during a misfire.

Backfiring occurs when unburned gasoline left the cylinder on the exhaust stroke and is ignited by the spark of the next cylinder farther down the system.

Because a four-cylinder car now only has three operating cylinders, you may detect a shift in overall engine sound if one cylinder is not working at all.

Engine Misfire When Accelerating

When an engine misfires when accelerating or when the throttle is squeezed, it is not only harmful for the engine, but also for everyone on the road. When a vehicle is under load and speeding, misfires can occur. This results in slow or sluggish acceleration, and your car may struggle to accelerate. When you press down on the throttle, you might sense a jerking action.

Worn-out spark plugs are the most typical cause of an engine misfire when accelerating. Excessive wear on spark plugs prevents them from igniting the fuel in the piston cylinder when they are supposed to. Foul spark plugs, a damaged distributor cap, or defective spark plug wires can also cause this. All of these issues result in the same result: the coil voltage does not jump the spark plug gap, causing the engine to misfire when the vehicle accelerates.

Many cars with a faulty throttle position sensor (TPS) and filthy fuel injectors are also reported as misfiring by their owners. Many other systems, like the fuel injection and air intake systems, rely on the TPS for accurate data, and if it fails, you may notice an engine misfire when accelerating, an illuminated check engine light, and the car may enter ‘limp home mode.’

Misfire At Idle Only

It’s fairly uncommon for an automobile to drive just fine while idling, but suddenly show evidence of minor hiccups or misfires. Because it doesn’t always report a diagnostic code, this can appear to be tough to figure out what’s causing it. Some mechanics may be hesitant to go more because they believe that if there is no code, there is no problem – but this is not the case. If experts can’t pinpoint the exact cause of the misfire at idle, they may wish to repair the fuel pump, injectors, and spark plugs as a precaution.

An improper air/fuel mixture is the most common cause of a misfire at idle, according to our findings. A defective O2 (oxygen) sensor, a single injector that needs cleaning, or even a vacuum leak can cause this. If the car has minor backfires, if the engine revs aren’t steady, or if any peculiar noises are coming from the engine bay, such as a hissing sound that suggests a vacuum leak, further physical indications will need to be addressed to track down the problem.

An engine misfire can be stressful for a vehicle owner since it makes driving more difficult. If your mechanic says they’re not sure what’s causing the problem, you’ll be even more stressed. Gathering as much information as possible about any problems you’ve had or symptoms that something is amiss with your engine might assist your mechanic in determining the reason of your misfire.

How do you clean diesel injectors?

A diesel fuel cleaner additive is the finest approach to clean fuel injectors on a regular basis. This can be put to the fuel tank on a regular basis to keep your engine running smoothly. It can keep dirt and debris from building up in your fuel injection system if done on a regular basis, perhaps once or twice a month.

How often should diesel injectors be replaced?

The fuel injection system is an important part of any diesel engine. The fuel is pressurized and injected into compressed air in the combustion chamber via this system. Feeding fuel to the injectors, regulating the fuel supply, modifying the injection time, and atomizing the fuel are all operations of a fuel injection system.

The proper amount of fuel, at the right time, in the right condition for combustion, must be delivered.

Fuel injectors help enhance fuel efficiency, reduce the need for fuel system maintenance, and keep emissions cleaner. A diesel fuel injector has an average lifespan of 100,000 kilometers. The nozzle and the injector body are the two primary elements of a standard fuel injector. If either of these components becomes clogged or destroyed, the vehicle’s overall performance is jeopardized.

  • Uneven idling or difficulty starting the car. The engine cranks, but it won’t start unless you crank it hard enough. On idle, the engine uses a variety of rev levels.
  • Misfire. A full diagnostic of a vehicle that is misfiring on ignition entails determining which component of the combustion process is missing. This is caused by either a lack of fuel injection or a lack of combustion chamber heat in a diesel engine. One of the cylinders’ fuel charge fails to ignite, or the fuel supply to the ignition system is insufficient.
  • There’s a strong odor of gasoline. The scent of diesel within the cabin indicates that there is a leak. This could be caused by a malfunctioning injector that allows fuel to leak out while it isn’t in use.
  • Emissions are filthy. Filters that are clogged and deposits on injectors create an uneven or partial fuel burn, resulting in a polluted environment around the exhaust and the discharge of white smoke from the exhaust pipe.
  • Fuel consumption has increased, while miles per gallon has decreased. Faulty injectors waste more fuel and have a direct impact on the performance and efficiency of your vehicle.

Clean fuel injectors are essential for your diesel engine to run at its best. Any of the following signs could suggest an issue with your fuel injectors, which should not be overlooked. Injectors that are unclean, clogged, or leaky are examples of this. If you’ve driven your car for more than 100,000 miles without replacing the fuel injectors, it’s time to have them looked at by a specialist.

How can I find out what is causing my misfire?

As previously stated, a misfire occurs when one or more cylinders fail to ignite properly or at all. Misfiring occurs when the combustion process, which involves the ignition of the air-fuel mixture that enters the cylinder, is disrupted in some way.

  • a failure of a component in the ignition system (including abnormal ignition timing advance),
  • Key valves or sensors that the automobile computer utilizes to calculate the correct air-fuel ratio are malfunctioning.

Misfires caused by a lack of spark, rather than a lack of fuel, are especially dangerous because unburned fuel can enter the exhaust system and catalytic converter.

If this happens, the raw fuel will eventually ruin the converter, necessitating immediate attention to the problem. If a misfire threatens to destroy your catalytic converter, the Check Engine Light (CEL) or Malfunction Indicator Light (MIL) will begin to flash on most modern vehicles.