May 26, 2011
Updated: July 24, 2014
Written by: Abraham Torres-Arredondo
Testing a misfire code (P0300, P0301, P0302, P0303, P0304, P0305, P0306) on your 2.7L, 3.2L or 3.5L Chrysler vehicle is not that hard to do, and in this article, Im gonna present to you some testing tips and techniques that will help you find the source of the misfire.
Since this article is divided into several different parts, here are the main points of this article:
- What Is a Misfire Condition?
- What Causes a Misfire Condition?
- Where to Start Your Misfire Diagnostic.
- Is this something I can do? or Do I need to take it to a shop?
- Where do I find the test articles?
What Is a Misfire Condition?
A misfiring engine, is an engine thats not firing on all cylinders. In the case of the 2.7L, 3.2L or 3.5L V6 engine, this usually means that one or two cylinders are ‘dead’.
Here are a couple more specific symptoms your Chrysler 2.7L, 3.3L, or 3.5L V-6 vehicle may/will experience when it's suffering a misfire condition:
- The check engine light will be on.
- One or more misfire codes (P0300 - P0306) will be stored in the car or pick up's computer's memory.
- 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.
- Misfire is present, but no misfire codes are registered in the Computer's memory and/or no Check Engine Light (CEL) on.
- 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.
What Causes a Misfire Condition?
The engine in your car needs Fuel, Air and Spark in each engine cylinder to run smoothly. When one or more cylinders start to misfire, the cause could be in any of following Systems:
Ignition System: The Ignition System has to deliver spark to each cylinder. The Ignition System is usually the culprit behind 90% of the misfire conditions.
The most common ignition system faults are:
- Spark Plugs.
- Spark plugs that are too worn.
- Spark plugs with broken ceramic insulators (usually broken while installing them during a tune-up or when a hot engine is power washed).
- Carbon fouled spark plugs due to the engine burning oil.
- Spark plugs that are swimming in oil from leaking valve cover spark plug tube seals (this is very, very common).
- COP Ignition Coil Boots.
- COP Coil boots that have carbon tracks on the inside.
- COP Coil boots that are soaked in engine oil from leaking valve cover spark plug tube seals.
- COP Ignition Coils.
- Each cylinder has its own ignition coil. These are known as Coil-on-Plug (COP) ignition coils... and they don't last forever.
Fuel System: Each engine cylinder has a fuel injector injecting fuel into it. If one or more fuel injectors goes BAD or becomes clogged... you'll have a bona-fide misfire condition on your hands.
Here are some other fuel system problems that can cause a misfire (‘dead’ cylinder, rough idle, etc.):
- PCM (Powertrain Control Module).
- The PCM can go BAD and can stop activating one or more fuel injectors.
- Electrical ‘Open’ Shorts.
- What usually happens, is the wiring harness starts to rub against a hard edge... which rubs off the wires' insulation, leading to an open or shorted circuit to ground.
Engine Mechanical Condition: An engine cylinder that is not producing enough compression, even it has the Spark and Fuel, will cause a misfire condition that will set a misfire code. Another thing that will cause a misfire (normally at idle) is vacuum leaks coming from a large vacuum hose or the intake manifold gasket.