Engine Cylinder Power Balance Test Explained

Engine Mechanic Camshaft Valves

A cylinder power balance test helps you find which cylinder is not contributing enough power to the engine, causing performance issues such as engine misfire or lack of power. The balance power test will point out if a cylinder is weak and not contributing its share to the total engine output. The power balance test can be performed on any vehicle, including 4, 6, 8, 10, and 12-cylinder engines, with the YOUCANIC full system scanner.

We see the engine power balance tests performed more often on 6-cylinder, V8, and V12 engines, as those engines typically have fewer issues when only one cylinder is underperforming. In contrast, on a four-cylinder engine, the engine and car will often shake if you have one underperforming cylinder.

On a V8, V10, or V12 engine, sometimes all you notice is an engine that is intermittently missing when idling, and in some cases, that miss can be hard to notice, especially if the check engine light is not on.

What is a cylinder power balance test?

Ford Spark Plug Ignition Coil Replacement 4-Cylinder Engine

Each cylinder should contribute equal power to make up the engine’s total power output in a healthy engine. The total output of an engine is equal to the sum of power produced by the individual cylinders. The cylinder power balance test considers the cylinder’s effect on engine speed to determine power.

Suppose the engine is running. A spark plug or fuel injector is disabled while the engine is running, which prevents the spark plug from firing that cylinder. Engine speed should decrease when the cylinder is not firing, therefore, not contributing to the engine power output. The decrease in engine speed (RPMs) is recorded and compared to the drops that occur when the other cylinders are disabled. If one of the other cylinders of an engine produces a lower engine RPM drop, then you have found the cylinder that has a problem.

The starting point is finding which cylinder is not contributing to the engine’s total power output. When one of the cylinders is not contributing as much power as the other cylinder, a mechanical, electrical, or fuel supply problem is affecting the cylinder to produce less power than the rest.

Cylinder Power Balance Test

An engine power balance test is an engine diagnostic procedure used to determine if all the cylinders are working well. The power balance test checks if all the cylinders are contributing equal power.

A power balance test is performed by disabling one cylinder at a time while measuring the drop in engine speed (RPMs). Cylinders can be disabled by turning off fuel injectors one at a time.

Symptoms

  • The engine may miss at idle
  • Check engine light may be on (not always)
  • Engine shaking at idle
  • Difficult accelerating

How do you perform a power balance test?

Direct Fuel Injector

You can use an advanced diagnostic scanner such as the YOUCANIC scanner to perform a power balance test. You can cancel one cylinder at a time and monitor the RPM drop during the procedure. While it is possible to perform this test without any tools, an advanced scanner can help you monitor and graph the RPMs as you disable one cylinder at a time.

You can perform a power balance test in a couple of different ways. The easiest way is with YOUCANIC full system scan tool. Some vehicle manufacturers have preprogrammed the ECU to carry a power balance test, while others do not. Don’t worry; with the YOUCANIC scanner, you can carry out the power balance test regardless of whether the car manufacturer has this program in the ECU.

You should see the RPMs drop when you disable one of the cylinders. The RPM drop should have the same effect as you disable each cylinder. The two most common ways to disable one cylinder from misfiring are to disable one of the ignition coils or fuel injectors if each cylinder has its injector. Disabling fuel injectors is the preferred method, so you don’t send raw fuel to the catalytic converter and cause problems. As a cylinder is disabled, you must monitor the RPM drops from the idle speed of 800-1000 RPM.

  1. Plug the YOUCANIC scanner into the OBD2 port under the dashboard. Chevrolet OBD2 Port Location
  2. Turn on the scanner and ignition, then select Maintenace on the scanner. YOUCANIC UCAN2 Scanner Home Page
  3. Select Power Balance from the menu. YOUCANIC UCAN2 Scanner Maintenance 2
  4. Select your make and model or Smart VIN. YOUCANIC UCAN2 Scanner Smart Vin or Select Model Chasis
  5. Run Power Balance Test.

The test under Maintenace is mainly for Ford and Mazda vehicles with power balance tests programmed in their ECUs. If your vehicle is not listed under the cylinder power balance test menu, follow these steps:

  1. Locate the injector for each cylinder or the spark plugs.
  2. Use the YOUCANIC scanner to disable one injector at a time.
  3. Record the engine RPMs and power output as you unplug each cylinder.
  4. Repeat the process for each cylinder.
  5. Compare the power output for each cylinder to determine if there are any imbalances or issues with the performance of the cylinders.
  6. One cylinder’s engine RPM drop will be less than the others, which means that the particular cylinder does not contribute enough power to the engine output; therefore, something is wrong with that particular cylinder.

It is important to follow the manufacturer’s recommendations and guidelines when performing a cylinder power balance test and to use caution when working on an engine. If you are not comfortable or experienced with working on vehicles, it is recommended to have a mechanic perform the test.

Performing Cylinder Power Balance Test without a Scan Tool

Nissan Sentra Fault Code P0300 Engine Misfire Ignition Coil Replacement

It is possible to perform a cylinder power balance test without a scanner, but you must be extremely careful so that you don’t get shocked or injured during the procedure.  In addition, monitoring the RPMs without a scan tool is more challenging. 

It is not a difficult task if you have a coil-on-plug design type, meaning each cylinder has an individual ignition coil. Unplug each coil one by one and check for RPM drop. Assuming you do not have a coil-on-plug type, you can remove the spark plug boots one by one. You need to be careful doing this, as you may cause a considerable shock if you’re not careful. To prevent getting shocked is to use a pair of plastic pliers.

Catalytic-Converter-Glowing

Also, injectors still send fuel to that cylinder when you perform the power balance test without a scan tool and disconnect the spark plug. The raw fuel hits the catalyst unburned and self-ignites in the catalytic converter. When you run a power balance test by disconnecting the spark plugs, especially if you do so for a long time, you risk causing damage to the catalytic converter.

Troubleshooting Tips

Porsche Worn Spark Plug

Once you have identified the underperforming cylinder, the next step is to find out why. There are a few things that you should check. For several possible issues, a cylinder may not output as much power as the other cylinders. Some common problems that can lead a cylinder not to perform well include:

  • Faulty spark plugs
  • Bad ignition coil
  • Vacuum leaks
  • Ignition Problme3s
  • Fuel pressure issue
  • Lifter or valve issue
  • Mechanical problems
  • Blown head gasket
  • Cracked head or block

Sometimes the problem may affect more than one cylinder. If that is the case, the cause could be several other issues, such as:

  • Dirty mass air flow sensor
  • Faulty oxygen sensor
  • Clogged catalytic converter
  • Electrical wiring issue
  • Defective Engine Control unit (ECU)

Several issues can cause an engine to be off balance, and troubleshooting the problem will depend on the specific symptoms and underlying cause.

Here are some steps you can take to troubleshoot an engine that is misfiring:

  1. Check the spark plugs and spark plug wires to ensure they are in good condition and properly connected.
  2. Check the fuel system to ensure it is functioning properly and delivering the correct amount of fuel to the cylinders.
  3. Check the air filter to make sure it is clean and not clogged.
  4. Check the exhaust system for any leaks or blockages.
  5. Check the engine’s ignition system to ensure that the ignition coils and control module are functioning properly.
  6. Check the compression of each cylinder to ensure that the engine is not experiencing any issues with sealing or compression.
  7. If you are still experiencing issues after checking these items, you may need to consult the manufacturer’s service manual or a mechanic for further troubleshooting and diagnosis.

It is important to use caution when working on an engine and follow the manufacturer’s recommendations and guidelines when troubleshooting a malfunctioning engine. If you are not comfortable or experienced with working on vehicles, it is recommended to have a mechanic perform the troubleshooting and repairs.

Spark Plugs / Ignition Coil

spark plug gap

Place a spark plug tester inline between the ignition coil and spark plugs. While the engine is running, the spark plug tool should spark. Repeat this procedure for each spark plug.

The quick and dirty method was to remove the spark plug and connect it to the ground to check the spark, but this method can be risky and cause injuries if not performed properly.

Injector

Fuel Injector

Use a stethoscope on the fuel injector for the underperforming cylinder and listen if you can hear it. Click. If the injector doesn’t click like the rest, that fuel injector is faulty. It may not be a good test if the vehicle has DIRECT fuel injection.

Compression

Engine Valve Closed

If you have determined that one cylinder is not contributing enough power to the engine output, use a compression and cylinder leakage test to determine if the problem is due to a compression issue.

Compression problems quite often are caused due to burned valves but also can be due to excessive carbon build-up on the valves. Other possible causes include worn piston rings, timing issues, and damaged valves.

Oxygen Sensors

Oxygen sensor chevy

If you are having issues with cylinders \underperfrming on one side of the engine (bank one or bank 2), but the other side is performing well, the problem could be a corresponding faulty bank oxygen sensor 1. The bank one sensor one and bank two sensor 1 data is used by the Engine Control Unit (ECU) to adjust the stochiometric ratio or, as it is commonly known, the fuel-air ratio. If data from the upstream oxygen sensor is wrong, the ECU will cause the engine to run too rich or lean.

Oxygen sensors are not the other issue that can cause one bank to run rough; other possible causes include a clogged catalytic converter or faulty mass air flow (MAF) sensor if the vehicle uses two MAF sensors.

Frequently Asked Questions

Should I perform a power balance test by disabling the ignition or fuel to the cylinder? 

The best way to perform a power balance test on vehicles with a catalytic converter is by disabling the fuel in the cylinder. If you disable the ignition side (spark), fuel will still make it to that cylinder and exit it unburned. The fuel will enter the catalytic converter, where it will most likely self-ignite, which can lead to premature failure of the catalyst.

Should I unplug the spark plugs or unplug the injectors?

Unplugging the fuel injectors when possible is better than unplugging the ignition coils. You are not sending unburned fuel to the catalytic converter by unplugging the injectors.

Will my car have misfire codes if there is a power balance issue?

Not always. While in many cases, a DTC such as P0300, P0301, P0302, P0303, etc., is set when a cylinder is not firing, intermittent misfires can sometimes not trigger a misfire code, which means that when you read the fault codes with the YOUCANIC scanner, there will be no fault codes pointing to a cylinder misfire.

My car misses at idle but has no check engine light on.

In some cases, the cylinder is still firing but is not working very well, therefore not putting out enough power. In that case, you need to do a power balance test to determine the offending cylinder. While the engine runs, you can cancel one cylinder at t time using the YOUCNAIC scanner, disabling each injector, and then monitor the RPM drop. Each cylinder in healthy condition will cause RPMs to drop the same RPMs. You have found the offending cylinder if you come across one cylinder that causes very little or no RPM drop when the cylinder is canceled by disabling the fuel injector. Next, you need to focus your diagnostic on that particular cylinder to find out why it is not working as well as the rest. First, check the cylinder’s fuel injector, spark plug, and ignition coil.

What scan tool do I need to do a power balance test?

The YOUCANIC full system scanner can be used to carry power balance procedure.

Can I use FORScan to perform a power balance test?

FORScan is a software scanner for Ford, Mazda, Lincoln, and Mercury vehicles for diagnostics purposes and also for carrying out the power balance test. The same procedure can be carried out with YOUCANIC full system scanner.

What scanner can I use to carry the power balance test?

You can use the YOUCANIC full system scanner.

Can I perform a power balance on my car?

A power balance test can be performed on any vehicle. The test can be performed on diesel and Duramax engines, Ford 6.7 engines, F150, GM vehicles, European vehicles, BMWs, Mercedes-Benz, and almost any vehicle.

Is a compression test and a power balance test the same thing? Which is better?

Both tests are often used to check the health of an engine, but these tests reveal very different issues. Compression test measures the compression of each cylinder and is often used to determine if the engine has a lot of wear. A power balance test is used to determine if there is a problem with one of the individual cylinders. If you are buying a car, performing a compression test is recommended.

How to do a power balance test FORSCAN?

Forscan is a diagnostic software tool that allows users to access and diagnose various vehicle systems, including the engine. To perform a power balance test using Forscan, you will need a computer with the Forscan software installed and a diagnostic adapter compatible with your vehicle.
Here are the steps to perform a power balance test using Forscan:
1. Connect the diagnostic adapter to your vehicle and to your computer.
2. Start the Forscan software and select your vehicle from the list of supported models.
3. Follow the prompts to connect to the vehicle’s computer.
4. Select the “Power Balance Test” option from the menu once connected.
5. Follow the prompts to initiate the power balance test. This may involve selecting specific cylinders or running the test on all cylinders.
6. The Forscan software will display the power balance test results, including each cylinder’s relative power output.
It is recommended to review the user manual carefully and any documentation provided with the Forscan software to ensure proper use and to familiarize yourself with the features and functions of the tool. If you are not comfortable or experienced with using diagnostic tools or working on vehicles, it is recommended to have a mechanic perform the power balance test.

Additional Resources

  1. Cylinder power balance test – autoedu.info
  2. Cylinder Balance Test – freeasestudyguides.com
  3. SOLVING AUTOMOTIVE PERFORMANCE ISSUES – ericthecarguy.com
  4. MASTERING THE BASICS: COMPREHENSIVE ENGINE TESTING – motor.com

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