Where To Start Your Misfire Diagnostic
The very first thing you have to do is identify which engine cylinder is the one misfiring (in other words, the cylinder that's ‘dead’).
Once you have identified the dead engine cylinder, you can proceed with a specific test to see if the problem is caused by a component from the ignition system or the fuel system or an engine mechanical condition.
You can identify the ‘dead’ cylinder by:
- Reading the misfire diagnostic trouble code(s) stored in the PCM (Powertrain Control Module= Fuel Injection Computer) with a scan tool or a code reader.
- Identifying the engine cylinder the misfire trouble code is accusing of misfiring (with an illustration like the one in the image above).
The following are my recommendations as to what to start testing first. Although you don't have to follow the list in that particular order:
STEP 1: Find the ‘dead’ cylinder first. If your 3.2L or 3.5L Chrysler vehicle is OBD II equipped (which comes with misfire diagnostics capability), connect a scan tool to read any misfire codes or other diagnostic trouble codes.
A misfire, unfortunately won't always set a diagnostic trouble code. In these cases, you'll need to do a cylinder balance test to find out which cylinder or cylinders are misfiring.
If your vehicle does not have OBD II (which means it's older than 1995), you'll definitely have to do a cylinder balance test (which involves disconnecting one fuel injector or coil at a time to see which one is the dead cylinder).
STEP 2: Check the COP ignition coil for spark. In most cases, a lack of spark from the ignition coil is the cause of the misfire issue. You can quickly determine this by testing the ignition coil with a spark tester.
I want to emphasize that testing the ignition coil with a spark tester is the only way to get a true spark result.
STEP 3: Check the COP ignition coil and spark plug and see if they're swimming in engine oil. If the ignition coil is sparking, remove and visually check the Coil-On-Plug coil and spark plug to check for:
- Wear and tear.
- Carbon tracks.
- Engine oil.
It's a very common problem for the valve cover spark plug tube seals to leak engine oil onto the spark plug and COP ignition coil boot.
This engine oil will eventually carbonize and divert the ignition coil's spark and cause a misfire.
The following case study will help you identify what carbon tracks look like:
- Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
STEP 4: Check the ‘dead’ cylinder's compression. If your ignition system tests come up dry, then next step is to make sure the cylinder, that's misfiring, doesn't have low compression.
STEP 5: Check the ‘dead’ cylinder's fuel injector. Fuel injectors go bad, and when they do, you'll have a misfire on your hands.
The above list of steps may seem/sound like troubleshooting a misfire is a complicated thing, but since everything on the 2.7L, 3.2L and 3.5L Chrysler engines is right on top and and in plain view, testing for a misfire is usually a breeze.
Is This Something I Can Do? Or Do I Need To Take It To A Repair Shop?
Most of the tests you'll need to perform are simple and easy. Even someone with little practical ‘wrenching’ experience can easily accomplish them.
The ignition system tests (like testing the COP coils) are found online just about anywhere. And as mentioned before, the ignition system is usually behind the misfire or rough idle condition on these Chrysler engines.
But even if you had to check the fuel injectors or engine compression, you can still accomplish these tests yourself.
The deciding factor, to either troubleshoot the vehicle yourself or take it to an auto repair shop, is if you have or don't have the necessary tools and the time required to perform the tests.
Here are a couple of questions to consider:
- Do I have all of the required info (such as repair manual, online testing info, etc.) to diagnose/troubleshoot the vehicle myself?
- Do I have the patience to work on my own car?
- What level of ‘wrenching’ experience do I have?
- Do I have the time to invest in troubleshooting and then repairing the issue? Or am I pressed for time?
Where Do I Find The Test Articles?
OK, here's what you signed up for! The actual testing information you need to get to the bottom of the misfire condition:
For the Coil-On-Plug ignition coil tests, these are found here: How To Test The COP Coils (Chrysler 3.2L, 3.5L) (this article is found at: easyautodiagnostics.com).
For the fuel injector tests, you can follow the testing instructions in this article (they're the same for the 3.2L and 3.5L engines, although the cylinders are numbered differently): 3.8L GM Fuel Injector Test.
For the engine compression test, you can follow the testing instructions in this article (they're the same for the 3.2L and 3.5L engines, although the cylinders are numbered differently): 3.8L GM Engine Compression Test.
If you need the info to perform a cylinder balance test on your vehicle, I still haven't written one for the 2.7L, 3.2L or 3.5L Chrysler engine but you can read the one I have written for the Ford 4.6L and 5.4L engines, since it's the exact same procedure. You can find the test here: Ford 4.6L, 5.4L Cylinder Balance Test (this test is at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!