Where to Start Your Misfire Diagnostic
The very first thing you have to do is to 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 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.
This is usually accomplished by using a scan tool and reading the codes stored in the PCM (Powertrain Control Module= Fuel Injection Computer). Then, by using an illustration (like the one in the image viewer) to identify which cylinder is the one affected.
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... so it may be necessary 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 its 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. Most of the time, a misfire is usually caused by spark not reaching the spark plug, the next step is do some spark tests with a spark tester. Using a spark tester is the only way to get a true spark result.
STEP 3: Check to see if the COP ignition coil and/or spark plug is swimming in engine oil. If you're getting spark, then I would start removing and visually checking the Coil-on-Plug coil and spark plug to check for wear and tear, carbon tracks, engine oil, etc (from the cylinder that was identified as having the misfire).
It's a very common problem for the valve cover spark plug tube seals to start leaking engine oil onto the spark plug and COP ignition coil boot.
STEP 4: Check the ‘dead’ cylinder's compression. If your ignition system tests come up dry, then next step is to make sure that 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... this is one of the few engines that 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 that 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... these are things that you can still accomplish yourself.
The deciding factor, to either troubleshoot the car or pick up yourself or take it to an auto repair shop, is if you have or don't have the necessary tools (and, depending if you live in the US, you can run down to your local auto parts store and rent them from them for free) 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..) 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, this 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 its the exact same procedure. You can find the test here: Ford 4.6L, 5.4L Cylinder Balance Test (this test is at easyautodiagnostics.com).