Quite a few things can cause your OBD II equipped 4.7L V8 Dodge Dakota (or Durango) to misfire and in this tutorial, I'll cover the most common causes of a misfire condition (and misfire trouble codes).
I can tell you from personal experience that testing a misfire condition isn't very difficult, so if you have a misfire trouble code, this is the tutorial that you need.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Una Falla En Cilindro (2000-2003 Dodge Dakota) (at: autotecnico-online.com).
What Is A Misfire Condition?
In a nutshell a misfire condition simply means that one or more cylinders on your 4.7L V8 engine are 'dead'. And by 'dead' I mean that they're not producing power.
So let's say you have two misfiring (dead) cylinders, the end result is that the engine is only running on 6 cylinders (instead of 8).
Even though it sucks that the engine is misfiring, the cool thing is is that the cause behind the misfire is usually one of three things. Either fuel is missing from the cylinder, or spark is missing from it, it's suffering a low compression problem.
Here are some of the things (symptoms) you'll see when your Dodge Durango is misfiring:
- If OBD II equipped, the check engine light will be on with one or more of the following misfire 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.
- P0307 Cylinder #7 Misfire.
- P0308 Cylinder #8 Misfire.
- Lack of power upon acceleration.
- Smell of unburned gas exiting the tail pipe.
- Rough idle and may stall.
- Cranks but does not start.
- Will not pass the emissions tests.
- Bad gas mileage.
Although the misfire codes don't tell you what exactly is the cause of the misfire or rough idle condition, it's possible to find out exactly what is causing it.
One of the most important things you need to know, to successfully diagnose a misfire or rough idle condition, is what causes a misfire. Let's go to the next subheading and find out.
What Causes A Misfire Condition?
As I mentioned before, a misfire is usually caused by one of three things: a lack of fuel, a lack of spark, or a compression problem in the misfiring cylinder.
To get into more specifics, here's a breakdown of the specific components that can cause your Dodge Dakota (Durango) to misfire:
Ignition System components and problems that cause a misfire when they fail:
- Bad or damaged spark plugs.
- Defective COP ignition coil.
- Carbon tracks on the spark plug and spark plug boot.
- Oil dripping (from the valve cover) onto the spark plugs and COP coil boots.
Fuel System components and problems that cause a misfire when they fail:
- Defective or clogged fuel injectors.
- Broken fuel injector connector.
- Electrical short in the fuel injector wires that are keeping the fuel injector pulse signal from reaching the fuel injector.
- This is usually the result of human error and after a major mechanical repair where the wiring harness was damaged.
- Defective fuel injection computer not pulsing the fuel injector (this is a very rare condition, but it happens).
- Defective fuel pump.
Engine Mechanical Condition problems that can cause a misfire.
- Worn piston rings causing a low compression problem.
- Worn cylinder head valves causing a low or no compression problem.
- Vacuum leaks from the intake manifold gaskets.
With this info under our belts, let's turn the page and find out what to test.
What Tests Can I Perform To Find The Cause Of The Misfire Condition?
Over the years that I've been working on cars, I've found that there's a specific and logical step-by-step way of diagnosing a misfire. Basically, it's a process of elimination —a series of targeted tests that help you zero in on the exact cause of the problem.
In this section, I'm gonna share that diagnostic strategy with you —along with links to the step-by-step tutorials that walk you through each test. I'm confident they'll help you figure out what's going wrong and what needs fixing.
STEP 1: Identify the dead cylinder. This usually means reading the misfire diagnostic trouble codes with a scan tool, then matching the misfire code to its engine cylinder using an illustration of the engine's layout.
If no misfire trouble codes are found, you'll need to do a manual cylinder balance test by unplugging one fuel injector at a time to see which one has no effect on the engine's idle.
Once you've found the 'dead' cylinder, the next step is to make sure its COP ignition coil is sparking.
STEP 2: Check the COP ignition coil for spark. Since most misfires are caused by a failed component in the ignition system, it's important to confirm that the misfiring cylinder is actually getting spark. You should:
- Perform a spark test (using a dedicated spark tester) on the ignition coil of the "dead" cylinder.
- Testing for spark with a spark tester is the most important first step —you'll know right away if the misfire is due to a lack of spark.
- How To Test The Ignition Coils (2000-2007 4.7L V8 Dodge Dakota And Durango).
- Check if the "dead" cylinder's ignition coil boot or spark plug is swimming in oil from a leaking valve cover gasket.
- If the coil is firing spark, remove the spark plug and inspect it for wear, carbon tracks, antifreeze contamination, or other signs of trouble.
- You can find out about carbon tracks here:
- Carbon Tracks Are A Common Cause Of Ignition Misfires (case study).
If all your tests indicate that spark is reaching the "dead" cylinder —and the ignition system components (spark plug, boot, etc.) all check out— then the next step is testing that cylinder's fuel injector.
STEP 3: Examine the spark plug and coil boot on the misfiring cylinder. The spark plug and its coil boot are common culprits behind a misfire —especially when worn or contaminated. You should:
- Remove the spark plug and inspect it carefully:
- Check for heavy carbon buildup on the electrodes —this can block the spark.
- Make sure the spark plug gap is correct —a gap that's too wide or too tight can cause weak or no spark.
- Look for signs of worn electrodes —severely worn plugs won't fire reliably.
- Inspect the spark plug well and the coil boot:
- Oil in the plug well is a red flag —usually from a leaking valve cover gasket.
- Oil contamination can cause arcing and prevent the coil from firing the plug properly.
- Check for carbon tracks on the ceramic insulator of the spark plug:
- Carbon tracks look like thin black lightning bolts —they cause the spark to jump to Ground instead of firing the air/fuel mixture.
- Carbon Tracks Are A Common Cause Of Ignition Misfires (case study).
The following case study is another real world example of how a misfire was diagnosed:
- Diagnosing A Toyota Corolla Misfire Case Study (at: troubleshootmyvehicle.com).
STEP 4: Test the fuel injector. If the ignition system is not the cause of the misfire, then the next step is to check the 'dead' cylinder's fuel injector.
You'll need to:
- Do a resistance test on the fuel injector to make sure it's internal coil does not have a short-circuit or an open-circuit.
- Do a Noid light test on the fuel injector's connector to make sure your Dodge's fuel injection computer is activating it.
- You can find the fuel injector resistance test here:
- Once you've confirmed that the fuel injector's internal winding is OK, you have one of two choices to make, either check it's spray pattern or check compression (I would choose checking compression, if compression is OK, then remove the injector and test its spray pattern):
If after making sure that the fuel injector's internal resistance matches the other 3 and that the fuel injection computer is activating it, the next step is checking the 'dead' cylinder's compression.
STEP 5: Test the compression of the cylinder. After eliminating the ignition system and the fuel system as the sources of the misfire, we now need to make sure that the 'dead' cylinder is compressing the air that's entering it.
You'll need to:
- Check all cylinders with a compression tester. You can find the test explained here:
- Check for vacuum leaks.
STEP 6: Check the intake manifold gaskets for vacuum leaks. The intake manifold uses rubber gaskets that will harden with time and cause vacuum leaks. These vacuum leaks will cause a rough idle condition (especially when the engine is cold) and eventually a misfire condition.
Troubleshooting a misfire is not a complicated thing. The key is to test the components and eliminate them as good or bad (and thus causing the misfire problem). Depending on your level of 'wrenching' experience, this is something that you can accomplish without taking it to the shop.
What Tools Do I Need To Test A Misfire?
To perform the misfire diagnostic tests mentioned in the previous section, you're gonna' need tools.
Depending on what the root cause of the misfire is, you may need several tools. Most of these you can buy online, none of these will break the bank and I'll make some recommendations on them. Here's a guide to some of the basic tools that can be and are used:
- Ignition System Tests:
- Spark tester.
- Multimeter.
- Test light.
- Fuel System Tests:
- Noid light.
- Fuel pressure gauge.
- Multimeter.
- Engine Mechanical Tests:
- Compression tester.
Keep in mind that using the right tool for the job will save you time, frustration, and /or keep you from damaging the component that you're testing.
More 4.7L V8 Dodge Dakota And Durango Tutorials
Want to dig deeper? The full index has all my step-by-step tutorials for diagnosing and fixing common issues on the 4.7L V8 Dodge Dakota and Durango —from misfires and no-starts to sensor and fuel system problems.
Here's a quick sample of what you'll find in the index:
- How To Test The Fuel Pump (2000-2007 4.7L V8 Dodge Dakota And Durango).
- How To Test The MAP Sensor (2002-2009 4.7L V8 Dodge Dakota And Durango).
- How To Test The Throttle Position Sensor (2000-2007 4.7L V8 Dodge Dakota And Durango).
- How Often Should I Replace The Spark Plugs? (2000-2009 4.7L V8 Dodge Dakota And Durango).
If this info saved the day, buy me a beer!
