Diagnosing the cause of the misfire (rough idle) on a 2.3L equipped Ford Mustang or Ranger (Mazda 2300) can seem quite daunting since you have 8 spark plugs and two coil packs to deal with.
Not only that, but quite a few things can cause a misfire condition (or misfire trouble codes).
In this tutorial, I'm gonna' present to you the basic causes of a misfire condition (rough idle) and a specific diagnostic strategy that will help you get to the bottom of the issue.
I'm also gonna' show you were you can find the specific test tutorials you'll need. Let's get started.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Un Falla En Cilindro (2.3L Ford Ranger y Mustang) (at: autotecnico-online.com).
Symptoms Of A Misfire Condition
Whether your specific 2.3L Ford Mustang or Ranger is OBD II equipped or not, a misfiring cylinder simply means that that cylinder is not pulling all of its weight.
In other words: If the engine is misfiring, the engine is simply not firing on all cylinders. Now, since the 2.3L Ford engine is a four cylinder, having just one 'dead' cylinder will cause an impact on engine performance and you're gonna' definitely feel it as you're driving down the road or stopped at a traffic signal.
Here are some of the most common symptoms:
- The check engine light (CEL) will be on.
- One or more misfire codes will be stored in the PCM's memory (if OBD II equipped).
- P0300 Random Cylinder Misfire.
- P0301 Cylinder #1 Misfire.
- P0302 Cylinder #2 Misfire.
- P0303 Cylinder #3 Misfire.
- P0304 Cylinder #4 Misfire.
- The engine is suffering a bonafide misfire condition, but no misfire codes are registered in the computer's memory (if OBD II equipped).
- 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?
Every cylinder, needs to have air, fuel, and spark to work. If any one of these components is missing from the equation, that cylinder will go dead. This means that so many different things can cause a misfire condition (or a rough idle condition). The cause of the misfire can be in any one of the following systems:
Ignition System: In a nutshell, the ignition system on the 2.3L Ford Mustang or Ranger consists of 2 ignition coil packs, an externally mounted ignition control module (certain years), spark plugs, and spark plug wires. The majority of misfire conditions have their root cause here.
- Bad spark plugs:
- Broken ceramic insulator.
- Center electrode's gap is closed due to carbon build up (from oil burning within the cylinder).
- Worn center electrode.
- Carbon tracks on the ceramic insulator.
- Bad spark plug wires:
- Spark plug boot is torn.
- Carbon tracks inside the boot.
- The metal terminal that connects to the spark plug is missing.
- Spark plug wire is so old that it's not transmitting spark anymore.
- Bad ignition coil pack:
- One or two towers (of the same ignition coil pack) are not firing off spark.
- Several towers from different coil packs are not firing off spark.
- Bad ignition control module:
- The ignition module is not activating one part of the coil pack and the end result is two 'dead' cylinders (since each coil pack is made up of 2 individual ignition coils that feed two cylinders with spark simultaneously).
- Not all 2.3L equipped Ford vehicles use an externally mounted ignition module, since in these vehicles, the PCM handles the 'ignition module' function internally.
Fuel System: The fuel system component that will usually cause a miss (misfire, 'dead' cylinder) is the fuel injector.
Here are some more specifics:
- Bad fuel injector(s):
- Injector is fried internally and does not spray any fuel.
- Injector is clogged and doesn't inject enough fuel.
- Injector is clogged/dirty and it's spray pattern of fuel doesn't atomize the gasoline correctly.
- Fuel injector is not being activated by the PCM.
- Fuel injector is not getting power (12 Volts).
Engine Mechanical Condition: The engine's internal condition is one of the most overlooked problem areas when diagnosing a misfire (rough idle, 'dead' cylinder).
An engine cylinder that is not producing enough compression (either because of worn valves or piston rings), even if it has spark and fuel, will cause a misfire condition.
Another thing that will cause a misfire (normally at idle) is vacuum leaks coming from a large vacuum hose or the intake manifold gasket.
- Low or no engine compression:
- One or two cylinders have low or no compression.
- Low or no engine compression will be the result of:
- Worn cylinder head valves.
- Worn piston rings.
- Blown head gasket.
- Bad intake manifold gasket:
- Leaking intake gaskets will not set a specific misfire code, if OBD II equipped, but will set a P0300 Random misfire code and a P0174 Lean condition trouble code.
What Tests Can I Perform To Find The Cause Of The Misfire Condition?
It is possible to find out exactly what's causing the misfire condition and/or misfire code on your 2.3L equipped Ford Mustang or Ranger (Mazda 2300).
The very first thing that has to be done, is to identify the cylinder that is misfiring (or dead), then you can go about doing specific tests to find out if it's being caused by a lack of spark or fuel or enough cylinder compression.
Finding out which cylinder is the one that's misfiring is pretty easy on the OBD II equipped vehicles, since the PCM will usually set a misfire code (P0301, P0302, P0303, P0304). On OBD I equipped 2.3L's, it's a little bit more challenging.
The following suggestions take into account if the vehicle is OBD I or OBD II equipped:
- OBD II: Read the diagnostic trouble codes with a scan tool. You should see a specific cylinder misfire code that will tell you what engine cylinder is the one being affected.
- There's a good chance, that even tho' your vehicle is OBD II equipped, the PCM will not set a specific misfire trouble code, when this happens, you'll need to do a cylinder balance test.
- OBD I: On older vehicles (that are not OBD II equipped), you'll need to do a cylinder balance test to find out the missing (dead) cylinder.
- The cylinder balance test involves disconnecting and connecting one fuel injector at a time to see if this has any effect on the engine's idle.
- If the cylinder is 'dead' to begin with (for any reason, like a lack of fuel or spark or low engine compression), when you unplug the fuel injector from its connector, you won't see any difference in the engine's idle.
- If the cylinder is OK, unplugging the fuel injector will 'cut out' the cylinder and you'll see/feel a difference in the engine's idle.
- NOTE: This test is done with the engine running and so you need to take all safety precautions and think and act safety all of the time.
- Test the ignition system first, this is whether you have a misfire diagnostic trouble code or not.
- Troubleshooting the spark plug wires.
- Troubleshooting the 2 ignition coil packs that feed the 8 spark plugs.
- Troubleshooting the spark plugs.
- Troubleshooting the ignition control module (ICM), if equipped.
- How To Test The Coil Packs, Ignition Module And CKP Sensor (1989-1994 2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).
- Test the compression of all engine cylinders.
- Testing the engine compression is a pretty fast test, since you only have to worry about 4 cylinders.
- Low engine compression in one or several cylinders is a common issue on high mileage engines.
- How To Test The Engine Compression (1989-1997 2.3L Ford Ranger) (at: easyautodiagnostics.com).
- Testing the fuel injectors. This involves:
- Checking the internal resistance of the fuel injector.
- Doing a Noid light test.
- Swapping fuel injectors to see if misfire moves.
- Check for vacuum leaks.
It seems like a long and complicated list, doesn't it? Well, don't worry, one of the most important things you need to successfully diagnose the misfire or rough idle on your 2.3L Ranger or Mustang is a diagnostic plan. The above diagnostic strategy is the one that I have used with a lot of success and it should also help you too.
What Tools Do I Need To Test The Misfire Code(s)?
Having the right tools to test and diagnose a misfire condition or misfire codes will make the difference between throwing money and time down the drain or saving money and time.
There's just no way around this, because with the right tools, not only are you gonna' save time and money, but you'll also save yourself a lot of frustration.
Depending on what the root cause of the misfire is, you'll 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.
Now of course, you'll also need basic hand tools like: screw-drivers, ratchet wrenches, sockets, etc. You'll also need a generic scan tool to retrieve the diagnostic trouble codes (DTCs) from the computer's memory. 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.
To help you troubleshoot the issue on your specific vehicle, each tutorial above (that I'm linking you to) will tell what tools you'll need and where to buy them.
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 deciding factor, to either troubleshoot your 2.3L Ford Ranger or Mustang 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?
- Do I have the time it will take to diagnose and repair the vehicle myself?
If this info saved the day, buy me a beer!
