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 at a glance:
- What Is A Misfire Condition?
- What Causes A Misfire Condition?
- What Tests Can I Perform To Find The Cause Of The Misfire Condition?
- What Tools Do I Need To Test A Misfire?
- More 4.7L Dodge Tutorials.
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.