How to Troubleshoot the Jeep Grand Cherokee 3.7 Misfire Problem?

Engine misfires are one of several typical issues that 3.7 engine owners of Jeep Grand Cherokees encounter. And this typically occurs when there is incomplete combustion in one or more cylinders. 

Keeping the issue unfixed for a long time can lead to costly repairs like engine failure. But no worries, we will help you figure out how to troubleshoot the Jeep Grand Cherokee 3.7 misfire problem.

What are the Common Symptoms of Jeep Grand Cherokee 3.7 Misfire Problems?

Your Jeep Grand Cherokee’s 3.7-liter engine may exhibit a number of symptoms that indicate misfiring. 

Among them, the reduction in engine power is the most prominent. Some of the other symptoms are; 

  • Engine idle
  • Poor fuel mileage
  • Check engine light
  • Excessive vibration
  • Black exhaust from the engine chamber
  • Strange sounds from the engine

What Causes the Jeep Grand Cherokee 3.7 Misfire?

You will find many essential components related to the engine chamber of your Jeep Grand Cherokee 3.7 engine. 

And it makes sense that even if single components malfunction, like the spark plugs, there will be an imbalance in combustion, which causes the engine to misfire. 

Bad Spark Plug

The spark plugs are critical internal combustion engine components as they ignite the air-fuel mixture. 

However, if the spark plugs in any cylinder go bad, it can most often cause interrupted combustion in the engine cylinder. 

And due to incomplete combustion, the internal combustion engine is supposed to misfire as there is an imbalance in the air-fuel-mixture. 

Bad Ignition Coils

There is a close connection between the spark plugs and ignition coils, which is why issues with the spark plugs can also affect them. 

The ignition coils play their part in transferring battery voltage to ignite the air-fuel mixture from the battery. 

And so, if the ignition coils go bad or are damaged, there won’t be enough battery power for spark plugs to ignite the air-fuel mixture. 

Due to this, there will be a lack of combustion, and the engine is supposed to misfire. 

Broken or Bad Vacuum Hose

The core duty of a vacuum hose is to deliver air into the engine cylinder of your Jeep Cherokee 3.7. 

But unfortunately, if the vacuum hose becomes damaged or broken, it can cause additional air to enter the engine cylinder. 

And when there is too much air in the engine cylinder compared to fuel, it creates an inappropriate air-fuel ratio, leading to incomplete combustion. 

The cylinders of your Jeep are not supposed to ignite the air-fuel mixture as expected. 

Faulty O2 Sensor

The O2 sensor on your Jeep Grand Cherokee signals the amount of air in the exhaust to the PCM. 

And then, your Jeep’s control unit determines the air-fuel mixture needed for improved combustion.

Sometimes, the 02 sensor of your Jeep becomes faulty, which can lead to an inappropriate signal received by the PCM about the amount of air. 

And thus, chances are there is too much air-fuel-mixture that can be too lean or rich, which can cause inappropriate combustion. 

Exhaust Manifold Leak

The exhaust manifold of your Jeep Grand Cherokee transfers the exhaust gas to the exhaust system. 

However, if there is leakage in the exhaust manifold, it can drive too much air into the engine intake system. 

And ultimately, this can cause a lean air-fuel-mixture, meaning there will be more air than fuel in the engine combustion chamber, which can cause incomplete combustion. 

Faulty Fuel Injector

The main job of the fuel injector in your Jeep Grand Cherokee 3.7 is to deliver fuel to the engine combustion chamber from the fuel line. 

But, when the fuel injector becomes clogged or dirty, the right amount of fuel can’t reach the engine chamber for proper ignition of the air-fuel-mixture. 

Or, it causes a lean air-fuel-mixture, which ultimately causes engine misfire due to imbalanced combustion.

Faulty MAF Sensor

A Mass Airflow Sensor (MAF) ‘s role differs from the O2 sensor on your Jeep Grand Cherokee 3.7. 

The MAF sensor monitors the air entering the engine cylinder and sends this information to the control unit of your Jeep. 

But when the MAF sensor becomes faulty, it cannot send proper information about the air entering the engine chamber to the control unit. 

And thus, there will be an improper air-fuel-mixture on the engine cylinder. The air-fuel mixture can be too rich or lean, which can cause the engine to misfire. 

Low Fuel Pressure

There are many causes behind the low fuel pressure in the engine. The fuel pump may go, or something is wrong with the filter. In addition, chances are there is an issue with the fuel line. 

And when there is low fuel pressure due to a lack of fuel in the engine chamber, the air-fuel mixture can be too lean. 

Due to excessive air and fuel in the engine chamber, incomplete combustion can occur, causing the engine to misfire. 

How to Troubleshoot Jeep Grand Cherokee 3.7 Misfire Problem?

Now you know the possible causes of engine misfires on your Jeep Grand Cherokee 3.7. In this part of the blog, you will see the solution to getting rid of the issue. 

Check and Replace the Bad Spark Plugs

You’ll probably notice the spark plugs in worn-out condition. In addition, spark plugs full of dirt, oil, and debris and covered with corrosion can be a common scenario. 

So, you should clean the spark plugs first. If cleaning doesn’t work, you need to replace it, which will cost you around $120-$380, including parts and labor costs.

Check and Repair/ Replace the Bad Ignition Coil

First, you should check the ignition coils carefully to see if there is any corrosion. Next, you have to clean the corrosion, if there is any. 

If cleaning the corroded ignition coils doesn’t work, you have to go for a replacement, which can cost you $180-$250. 

Here you can check this video to replace the ignition coils of your Jeep Grand Cherokee 3.7.

Check and Replace the Broken Vacuum Hose

You should carefully inspect any leakage in the vacuum hose near the engine chamber. 

If you find any leakage, it will be better to replace the vacuum hose, which can cost you around $20-$60 for parts and roughly $50-$100 for labor.

Check and Replace Faulty O2 Sensor

You will find the O2 sensor located near the catalytic converter. Once you discover the sensor, you need to check it carefully. 

In most cases, the O2 sensor can be seriously corroded or worn out. So, it is better to replace the O2 sensor after checking. 

The replacement task can cost you $130-$160 for labor and $250-$300 for parts. But you can perform the job on your own as well.

Check and Repair /Replace the Exhaust Manifold Leak

Depending on the condition of the exhaust manifold leakage, you may need to repair or change it. You can use a sealer to fix the leakage. 

To replace the exhaust manifold, you need to spend $1000-$1200 for parts and $300-$350 for labor. 

Check and Replace the Faulty Fuel Injector

You need to check for a clogged fuel injector and try to clean it. If cleaning the fuel injector doesn’t work and there is additional damage, you should replace the fuel injector with a new one. 

It will cost approximately $280-$350 for parts and $150-$180 for labor. Watch this video to learn about replacing the fuel injector on your Jeep Grand Cherokee 3.7 engine.

Check and Replace the Faulty Mass Airflow Sensor

Like the O2 sensor on your Jeep Grand Cherokee, the MAF sensor can be highly corroded or worn out. 

First, you should attempt to clean the MAF sensor. However, if the sensor is worn out, you need to go for a replacement. 

You can locate the MAF sensor near the intake manifold in your Jeep Grand Cherokee 3.7 engine.

To replace the MAF sensor, you might need to spend approximately $140-$170 for parts. In addition, it will cost you another $40-$80 for labor costs. 

Fix the Low Fuel Pressure Issue

First, you should identify exactly what causes low fuel pressure. Once you determine the core cause by checking the fuel pump, fuel filter, and fuel line, you can take steps to resolve them. 

The repair cost can vary depending on the component that causes the issue. It is better to contact a mechanic to check for issues related to low fuel pressure. 

You can watch this video to determine the fuel pressure of your Jeep Grand Cherokee.

Frequently Asked Questions

As engine misfire is a common issue with the Jeep Grand Cherokee 3.7, people often share their queries. Here, you will find the answers to some of them.

How can I tell which cylinder is misfiring on a Jeep Grand Cherokee 3.7?

You will find an OBD II scanner at the marker to help you determine the exact misfiring cylinder. You can also use an infrared temperature gun to know which cylinder is misfiring. 

Why is my car still misfiring after I change the spark plugs?

There are many causes behind engine misfires. So, even if you change the spark plugs, the fuel injector, 02 sensor, MAF sensor, or leakage in the vacuum system might happen. Therefore, you need to check these components as well. 

How can long spark plugs last on your Jeep Grand Cherokee 3.7?

The spark plugs on your Jeep Grand Cherokee are supposed to last around 30,000-60,000 miles. You must be careful about replacing spark plugs, which can cause significant engine issues. 

How often should you change the engine fuel of the Jeep Grand Cherokee 3.7?

It is recommended to change the engine fuel of your Jeep Grand Cherokee 3.7 after five years or 50,000 miles of use. You shouldn’t drive your Jeep with contaminated engine fluid.

Final Words

We suggest you be careful with your Jeep Grand Cherokee 3.7 engine. If you think you can’t change any components of the engine chamber on your own, take assistance from the mechanic to deal with an engine misfire. Replace the spark plugs, 02 sensor, fuel injector, etc, after a certain period.

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