Jeep Wrangler Engine Misfire (8 Causes & Fix)

Wondering what is the Jeep Wrangler engine misfire?

A Jeep Wrangler engine misfire occurs when one or more cylinders in the engine are not producing power. There are several reasons for this, such as a fuel injector can clog, a faulty spark plug, a faulty ignition coil, a vacuum leak, a clogged or faulty exhaust gas recirculation, a faulty crankcase ventilation valve, a faulty oxygen sensor, a clogged catalytic converter, or issues with seals and gaskets.

In this article, we will look at some causes and fixes for Jeep Wrangler engine misfiring, as well as its symptoms, codes, etc.

Jump to

Causes and Fix for Jeep Wrangler Engine Misfire

  1. Faulty Ignition Coil
  2. Faulty Spark Plug
  3. Clog Fuel Injector
  4. Vacuum Leak
  5. Clogged or Faulty Exhast Gas Recirculation valve
  6. Faulty Crankcase Ventilation Valve
  7. Faulty Oxygen Sensor
  8. Clogged Catalytic Converter
  9. Issues With Seals and Gaskets.

Read on for a guide about each cause of the Jeep Wrangler engine misfire, including the solution to each cause.

1. Faulty Ignition Coil

The ignition coil is an induction coil in a Jeep ignition system. The ignition coil is a kind of transformer that will convert the battery 12 volts into some 20,000 to 85,000 volts of electricity to induce a spark in the spark plug to ignite the fuel.

The ignition coil can be damaged because of a faulty or worn spark plug, vibrations, excessive moisture, or a reduction of the insulation between the primary and secondary coils, which causes overheating.

When there is a problem with the ignition coil due to any reason, it can’t produce the voltage necessary for the spark plug, resulting in a Jeep Wrangler engine misfire.


To fix or troubleshoot an ignition coil, read any fault codes and compare them with the correct functioning coil.

Check the coil for any damage, such as a crack in the housing or damage to the electrical wiring or plug connection.

Remove and inspect the spark plug. Check the plug wire and spark gap.

Use the multimeter to check the voltage supply to the ignition coil. A voltage should be more than 10.5 volts. 

Again, check the coil primary and secondary circuits with a multimeter. If the resistance is zero, it indicates a short-circuited coil, and a high or infinite reading indicates an open-circuited ignition coil.

A faulty ignition coil will cause a problem with the Jeep engine and catalytic converter. So, replace your faulty ignition coil as soon as possible.

According to repair pal, the average replacement cost of a Jeep wrangler ignition coil is between $220 and $276. The parts cost between $125 and $156.

2. Faulty Spark Plug

A spark plug is a device that fits into the engine’s cylinder head. The spark plug consists of two electrodes that are separated by an air gap, through which the current of high-tension discharge creates a spark, and this spark ignites the fuel in the combustion chamber.

The spark plug of the Jeep Wrangler can be damaged because of overheating, oil contamination, or carbon buildup on the tip.

When there iWhen there is a problem with the spark plug, the spark plug will not create a spark to ignite the fuel, causing the Jeep Wrangler engine to misfire.


If there is carbon buildup on the spark plug tip, use sandpaper to clean it. Check and repair the damaged, stripped spark plug thread.

The ordinary copper and nickel spark plug has a lifespan of 50,000 miles. and a platinum or iridium spark plug can last 60,000 to 150,000 miles.

You should change your spark plug after running the above-mentioned miles.

The replacement cost of a Jeep Wrangler spack plug is between $258 and $305. The parts are costs between $93 and $97.

3. Clog Fuel Injector

A fuel injector is a device that introduces fuel into the combustion chamber. The fuel pump provides the pressurized fuel. The fuel injector then automizes the fuel into a fine mist so it can burn easily in the combustion chamber.

A Jeep Wrangler’s fuel injector can clog due to contaminant buildup, leak due to dry, cracked rubber seals, or crack within the fuel injector.

When there is a problem with the fuel injector, the fuel injector will not provide fuel for combustion, resulting Jeep Wrangler engine misfire.


To repair the clogged fuel injector, add the fuel injector cleaners to the fuel.

Another way is ultrasonic cleaning of the clogged fuel injector.

A dead fuel injector that does not respond to the electrical signal is also considered clogged and can’t be repaired.

According to repair pal, the average cost of a Jeep Wrangler fuel injector is between $320 and $365. The parts cost between $189 and $200.

4. Vacuum Leak

The Vacuum leak is when some air bypass the engine air intake tract. In normal conditions, all air to the engine is routed through the electronic throttle control body.

A broken vacuum tube or hose, leaking actuators, solenoids, valves, leaking gaskets and seals, or a leaking brake booster are the causes of a vacuum leak.

When there is a vacuum leak, the air and fuel mixture are not in the right proportion for combustion, resulting in an engine misfire.


To diagnose and fix the vacuum leak, start with a visual inspection of the engine because the most common cause of a vacuum leak is broken vacuum tubes or hoses.

Do a smoke test to find the vacuum leaks.

Don’t use flammable fluid such as the starting fluid or brake cleaner to find the vacuum leaks.

The average repair cost of Jeep Wrangler vacuum leaks is between $150 to $1000, depending on the cause and location of the leak.

5. Clogged or Faulty Exhaust gas recirculation Valve

Exhaust gas recirculation (EGR) is a technique used in engines to reduce the emission of NOx. The EGR recirculates the engine exhaust gas back to the engine cylinder.

The EGR valve can clog because of the build-up of soot particles, carbon deposits, and dirt from fuel.

When the EGR valve is stuck open, then all the exhaust gas returns to the cylinder, and there is not enough oxygen for combustion. resulting in the Jeep Wrangler’s engine misfiring.


To fix the EGR valve, remove the valve and spray the EGR valve cleaner on the carbon deposits or soak the valve in the cleaning solution for a few minutes, and then remove the deposits with a pipe cleaner or wire brush.

If there is a lot of dirt on the EGR valve, it’s better to replace it.

According to the repair pal, the average replacement cost of a Jeep Wragler EGR valve is between $425 and $457. The parts cost between $306 and $307.

6. Faulty crankcase ventilation (PCV) valve

The positive crankcase ventilation (PCV) valve system removes unwanted gases from the crankcase and introduces filtered fresh air to the crankcase.

The PCV valve is exposed to extreme pressure and temperature, which can cause these parts to swell, stick in place, or even crack.

This will cause a vacuum leak, resulting in the Jeep Wrangler’s engine misfiring.


According to the repair pal, the average replacement cost of a Jeep Wrangler PCV valve is between $133 and $160. The parts cost between $72 and $82.

7. Faulty Oxygen Sensor

The oxygen sensor is an electronic device that measures the proportion of oxygen in gas or air. The oxygen sensor tells the vehicle’s ECU the right amount of air in the air and fuel mixture for combustion.

The oxygen sensor can fail because of buildup due to rich fuel mixture, oil blow-by, gasket leak, extremely high temperature, or O2 sensor wear over time. All these can affect the O2 sensor response characteristics.

When the oxygen sensor fails, it will not detect the correct proportion of air in the air and fuel mixture, causing an engine misfire.


You can not repair the faulty oxygen sensor. The straightforward solution is to replace the O2 sensor.

According to repair pal, the average replacement cost of a Jeep Wrangler O2 sensor is between $219 and $272. The parts cost between $154 and $190.

8. Clogged catalytic converter

The vehicle’s catalytic converter is an exhaust emission control device that reduces the harmful emissions from the internal combustion engine by catalyzing a redox reaction.

Means it converts harmful gases like carbon monoxide and hydrocarbons into less harmful ones like carbon dioxide and nitrogen.

The catalytic converter can overheat, melt, or break due to an engine misfire, low compression, or a poor spark plug.


You will clean the clogged catalytic converter using an additive cleaner such as Oxicat or Cataclean, which can help remove carbon buildup and unclog the converter.

According to repair pal, the average replacement cost of a Jeep Wrangler catalytic converter is between $1,875 and $1,956. The parts cost between $1,731 and $1,774.

9. Issues With Seals and Gaskets

The seals and head gaskets provide a seal between the engine block and cylinder head. It prevents coolant and oil from leaking and the engine from catching fire.

The constant exposure to high temperatures and pressures, vibrations, and contact with hot fluid over time will cause seals and gaskets to leak.

The leakage in seals and gaskets will cause a loss in engine compression and an engine misfire.


If the Jeep runs without overheating, it’s better to use chemical repair products to seal leaks.

According to the repair pal, the average replacement cost of a Jeep Wrangler head gasket is between $1,541 and $1,741. The parts cost $780.

Symptoms of Jeep Wrangler Engine Misfire

  1. Rough Idling
  2. Sluggish Acceleration
  3. Engine Sound Changes
  4. Black Exhaust
  5. Check Engine Light Might Illuminate

1. Rough Idling

When your Jeep misfires, you may notice rough idling. Rough idling means the vehicle’s RPMs jump up and down.

When the misfire occurs, the engine starts and stops suddenly, and you might have a bumpy driving experience.

2. Sluggish Acceleration

The Jeep Wrangler engine misfire also causes sluggish or poor acceleration.

Most of the time, misfires occur when your Jeep is under load conditions or when you are trying to accelerate.

When you try to accelerate the response, it is not what you expect. You might experience jerking motions when you step on the gas pedal.

3. Engine Sound Changes

When you hear “clanking,” “coughing,” or “sputtering” sounds coming from the engine, It means the internal combustion process has been interrupted due to an engine misfire.

An engine misfire is a serious problem; it will damage your engine. So, you should have your Jeep inspected by a mechanic as soon as possible.

4. Black Exhaust

When the Jeep emits black exhaust, it means the internal combustion reaction is interrupted due to an engine misfire.

5. Check Engine Light Might Illuminate

The check engine light in the Jeep dashboard illuminates when there is a problem with the engine.

When the engine misfires, the sensors that monitor the engine’s performance will tell the ECU that the engine is not functioning correctly, and the check engine light will illuminate.

Jeep wrangler engine misfire codes

P0300Multiple Cylinder Misfire
P0301Cylinder 1 Misfire
P0302Cylinder 2 Misfire
P0303Cylinder 3 Misfire
P0304Cylinder 4 Misfire
P0305Cylinder 5 Misfire
P0306Cylinder 6 Misfire


What Happens When a Car Misfires?

Symptoms Of An Engine Misfire And Causes

Jeep Wrangler JK Diagnostic Codes

What Is a Misfire and What Causes It?

Jeep Wrangler Engine is misfiring Inspection at your home or office.

Jeep Wrangler Ignition Coil Replacement Cost

Scroll to Top