How To Test A Misfire Problem (2004-2008 3.5L Malibu)

Testing a misfire condition that's lighting up the check engine light, with a misfire trouble code, can seem like a daunting challenge on the 3.5L Chevy Malibu.

The cool thing is that there's a specific diagnostic flow to testing a misfire condition (yup, there's a 'method to the madness' of testing a misfire condition).

In this tutorial, I'll explain some of the basics of testing a misfire condition that'll help you get to the bottom of the issue.

Symptoms Of A Misfire Condition

You're going to see two very specific things when your 3.5L Chevrolet Malibu is suffering a misfire condition.

The first one is the check engine light shining nice and bright on your Chevy Malibu's instrument panel. And it'll be shining nice and bright because of one or more of the following misfire trouble codes:

• P0300: Random Cylinder Misfire.
• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.
• P0305: Cylinder #5 Misfire.
• P0306: Cylinder #6 Misfire.

The other thing that you're gonna' see that your Chevy Malibu's engine will idle rough. You'll also see one or more of the following:

• The engine misses when you accelerate the vehicle down the road.
• The check engine light flashes when the misfire condition is present.
• The exhaust smells of raw gasoline.
• Bad gas mileage.

What Causes A Misfire Condition

The 3.5L V6 engine in your Chevy Malibu has 6 cylinders. Each cylinder needs air (compression), fuel, and spark to produce power.

So in a nutshell, a cylinder will misfire because it's missing either compression, or missing fuel, or missing spark.

On the 3.5L V6 Chevy Malibu, the most common cause of a cylinder misfire is a problem with the ignition system. To be a bit more specific, the following components will cause a misfire condition when they fail:

• A defective spark plug wire or wires.
• A bad ignition coil.
• A bad spark plug.

Of course the ignition system isn't the only system that can cause a misfire problem. The other components that can cause a misfire, when they fail, are:

• A bad fuel injector.
• A clogged fuel injector.
• A cylinder with low compression.
• A bad intake manifold gasket leaking vacuum.

The cool thing is that pinpointing the exact cause of the misfire boils down to doing a few specific tests. And that's what I'll discuss in detail in this tutorial.

What Tools Do I Need?

You'll need a few tools to be able to test a misfire condition. The cool thing is that the tools you'll be needing and using are not going to break the bank.

The basic misfire troubleshooting tools you'll need are:

• A spark tester.
• An engine compression tester.
• A multimeter.

You can borrow or buy most of these tools at your local auto parts store.

STEP 1: Find The Dead Cylinder First

The most important first step, when diagnosing a misfire condition on your 3.5L Chevy Malibu, is to find the cylinder that is misfiring.

This is probably the easiest part of the whole process because you can easily identify the misfiring cylinder by simply connecting a scanner or trouble code reader and checking for misfire diagnostic trouble codes.

Once you've got the misfire trouble code, you can use the above illustration to identify the cylinder on the engine itself.

Now in some cases, even though the engine is suffering a bonafide misfire the fuel injection computer will not set a misfire trouble code. In these cases you'll need to do a manual cylinder balance test. You can find this test explained in detail here: How To Do A Cylinder Balance Test (2004-2008 3.5L Malibu).

Once the the 'dead' cylinder has been identified, the next step is: STEP 2: Making Sure The Dead Cylinder Is Getting Spark.

STEP 2: Making Sure The Dead Cylinder Is Getting Spark

The ignition system components that are more likely to cause a misfire when they fail are:

• Ignition coil pack.
• High tension wire (spark plug wire).
• Spark plug.

Once you have identified which specific cylinder on your 3.5L Chevrolet Malibu is misfiring (dead), the next step is to find out if it's getting spark.

This can be very easily done by connecting a spark tester to the dead cylinder's high tension wire and checking for spark.

If spark is present, then you can conclude that the high tension wire and the ignition coil are okay and doing their job.

Your next step is to remove the spark plug and visually check it for any kind of damage that could keep it from firing off spark inside the cylinder.

If you get no spark, when you test the high tension wire for spark, then you'll need to test for spark directly on the ignition coil tower the high-tension wire connects to.

If you get spark at the ignition coil tower, then you can conclude that the high tension wire is defective. Now if you don't get spark (at the ignition coil's tower), then you can conclude that the ignition coil is defective.

If the misfire is being caused by a lack of spark, then replacing the component that's causing it will resolve your 3.5L Chevy Malibu's misfire.

NOTE: It's very important that you use a dedicated spark tester to test for spark. Testing for spark by any other means will give you a false test result of that will have you chasing ghosts and spending time and money on parts your Chevy Malibu does not need to solve the problem.

If the dead cylinder is getting is spark, then the next step is to check its fuel injector. Go to: STEP 3: Testing The Dead Cylinder's Fuel Injector.

STEP 3: Testing The Dead Cylinder's Fuel Injector

As mentioned before, if the dead cylinder is not getting fuel then it's going to misfire. And the one component charged with supplying the cylinder with fuel is the fuel injector.

There's a good chance that the fuel injector that supplies fuel to the dead cylinder is underneath the intake manifold plenum. The cool thing is that you don't have to remove it (the plenum) to test it or any of the other fuel injectors.

Testing the fuel injector of the dead cylinder simply involves testing its internal resistance with a multimeter (in Ohms mode).

The purpose of this resistance test is to see if the fuel injector's internal winding has fried. Because if the fuel injector's internal winding has fried then it's not going to inject any fuel.

Testing the fuel injector resistance is very easy to do on the 3.5L Chevrolet Malibu. Depending on the specific year model of your Malibu, take a look at one of the following tutorials:

• How To Test The Fuel Injectors (2004-2006 3.5L Malibu).
• How To Test The Fuel Injectors (2007-2008 3.5L Malibu).

If the dead cylinder is getting is spark and its fuel injector is OK, then the next step is to check for intake manifold leaks. Go to: STEP 4: Checking For Vacuum Leaks Around Intake Manifold.

STEP 4: Checking For Vacuum Leaks Around Intake Manifold

The intake manifold gaskets on the 3.5L V6 Chevy Malibu are made out of plastic. At around 60,000 miles or so, these plastic gaskets will start to disintegrate.

You'll usually see one of two things if not both when this happens:

• Coolant leaking from the ends of the engine where the intake manifold mates to the cylinder heads.
• A rough idle condition that lights up the check engine light with a P0300 Random Cylinder Misfire trouble code.

In a nutshell, checking for vacuum leaks involves two simple tests. The first one is visually checking the ends of the intake manifold to see if coolant leaking.

The second test involves spraying carburetor spray on the ends of the intake manifold.

If the intake manifold gasket is bad and is leaking vacuum. Then when you spray starting fluid or carb cleaner around the leak, the engine's idle (RPMs) will change.

This is due to the fact that the carb cleaner will change the air/fuel mixture when it gets sucked into the engine.

When performing this type of vacuum leak test you need to do it with a cold engine (as a safety precaution).

If your 3.5L Chevy Malibu's misfire is not being caused by a lack of spark, or a bad fuel injector, nor vacuum leaks, then the next step is to test the dead cylinder's compression. Go to: STEP 5: Testing The Compression Of The Dead Cylinder.

STEP 5: Testing The Compression Of The Dead Cylinder

Testing the compression of the dead cylinder, when diagnosing a hard to find misfire, is probably one of the most overlooked test when diagnosing a hard to find misfire.

What usually happens, when engine compression is causing a misfire, is that the dead cylinders compression is very low.

The rule of thumb is at any compression value lower than 15% of the highest compression value your engine has will cause a misfire problem.

Although it's recommended that you test the compression of all six cylinders, it really isn't necessary when you're trying to diagnose a misfire problem. Especially if you have already identified of a dead cylinder.

These are the steps I recommend you follow if you have identified the specific cylinder that's dead:

• Check the compression of the dead cylinder and one other cylinder that is not misfiring (dad).
• Multiply the highest compression number (which is the one you got from the non-dead cylinder) by 0.15.
• Subtract the product (of your multiplication problem) from the highest compression number.
• The difference from your subtraction problem, is the lowest compression number (value) that the dead cylinder can have. Any number (value) lower than this and the cylinder will misfire.

You can find the compression test explained in detail here:

• How To Test The Engine Compression (2004-2010 3.5L V6 GM Engine).

More 3.5L V6 Chevy Malibu Tutorials

You can find a complete list of 3.5L V6 Chevy Malibu tutorials here: GM 3.5L V6 Index Of Articles.

Here's a list of articles you'll find there:

• How To Test The Engine Compression (2004-2010 3.5L V6 GM Engine).
• How To Do A Cylinder Balance Test (2004-2007 3.5L Malibu).
• How To Test A Blown Head Gasket (2004-2007 3.5L Malibu).
• How To Test The MAF Sensor (2004-2008 3.5L Malibu).