Wednesday, June 18, 2014

1998 Chevy Cavalier Z24 2.4L LD9 Misfire Condition

Chevy Cavalier Z24 2.4L LD9 Misfire Condition. My 1998 Chevy Cavalier Z24 2.4L LD9 With 285,000K Has An Intermittent Misfire Condition After Using Fuel Injector Cleaner. My 1998 Chevy Cavalier Z24 Also Now Has:

  1. Intermittent Hard Starts.
  2. Intermittent Stalls.
  3. Intermittent Loss Of Power On Acceleration.
  4. Intermittent Mildly Back Fires On Down Shifting At Any Speed.
  5. Intermittent Mildly Back Fires After Removing Foot From Gas At Any Speeds Randomly After Using Fuel Injector Cleaner. 

My 1998 Chevy Cavalier Check Engine Light Turned On After Adding A Bottle Of Fuel Injector Cleaner ( I Read The Fuel Injector Cleaner Instructions ) And 70L Of Regular Gas To A Near Empty Tank In The City On A Rainy Day. I Usually Keep The Gas Tank At Least Half Full After Replacing The Fuel Pump About 10,000K Ago.


Uneventful 75K Later Down The Highway The Check Engine Light Came On And A Few Minutes Later The And , Now Has An Intermittent Misfire Condition And Now Has Hard Starts After Adding Blew The CEL Check Engtine Light After 75k On The Highway After I Added Fuel Injector Cleaner To A Full Tank And Filled Up. I Used A Scanner And Pulled The Following Codes.

4/9 - P0171 - SYSTEM TOO LEAN BANK 1
7/9 - P0172 - SYSTEM TOO RICH BANK 1

1998 Chevy Cavalier Z24 2.4L LD9 Misfire Condition. Sometimes, even tho’ the engine is suffering a bona-fide misfire, no misfire codes are registered and no check engine light (CEL) comes on.

What Tools do I Need to Test the Misfire Code(s)?

Finding the exact cause of the misfire codes or misfire condition is possible... with the proper tools. Without them, you won’t be able to diagnose /troubleshoot those issues on your Quad-4 equipped GM car.

Depending on what the root cause of the misfire is, you may 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:

  1. Spark Tester.
  2. Multimeter.
  3. Test Light.

Fuel System Tests:

  1. Noid Light.
  2. Fuel Pressure Gauge.
  3. Multimeter.

Engine Mechanical Tests:

  1. 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 (DTC’s) 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.

One of the most common problems that you or I are likely going to face with a Quad-4 equipped vehicle is a misfire condition. Although it stinks that your Quad-4 GM car is experiencing a misfire condition... the cool thing is that there’s a method to the madness of troubleshooting it.

In this tutorial, I’m going to explain in some detail the most common causes of misfires and misfire codes (P0300, P0301, P0302, P0303, P0304). And more importantly, I’m also gonna’ offer you a simple diagnostic strategy that I’m certain will help you nail down the cause of the misfire condition, misfire code, or rough idle condition your 1998 Chevy Cavalier Z24 2.4L Quad-4 GM car engine is experiencing.

What is a Misfire Condition?
What Causes a Misfire Condition?
How Can I Test the Misfire?
What Tools do I Need to Test the Misfire Code(s)?

What is a Misfire Condition?

As you’re already aware 2.4L Quad-4 engine has four cylinders. In a nutshell, each one of those four cylinders needs three things to produce power and they are: fuel, spark, and air (typically compression).
When your Quad-4 equipped GM vehicle is suffering a misfire... it’s because one of those three things is missing from one of the four cylinders. Simplified: A cylinder is misfiring because it’s missing fuel, or spark, or air (compression).

Since the 2.4L engines have only 4 cylinders, having just one of those cylinders misfire will have pretty obvious consequences due to the fact that the engine in your GM car is running on only 3 cylinders. If the engine in your car has one or two misfiring cylinders, you’ll have one or more of the following symptoms:

  1. The check engine light (CEL) will be on.
  2. One or more misfire codes (P0300-P0304) will be stored in your car’s PCM memory.
  3. P0300 Random Cylinder Misfire.
  4. P0301 Cylinder #1 Misfire.
  5. P0302 Cylinder #2 Misfire.
  6. P0303 Cylinder #3 Misfire.
  7. P0304 Cylinder #4 Misfire.
  8. Lack of power upon acceleration.
  9. Smell of unburned gas exiting the tail pipe.
  10. Rough idle and may stall.
  11. Cranks but does not start.
  12. Will not pass the emissions tests.
  13. Bad gas mileage.

Although the misfire codes don’t tell you what exactly is the cause of the misfire or rough idle condition... there is a way 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 in the previous heading, each of the 4 cylinders of your Quad-4 engine needs 3 things to be able to produce power. In a nutshell, these 3 things are:

  1. Air
  2. Fuel
  3. Spark

It’s when one of these three things is missing from the mix that the engine in your Quad-4 GM vehicle starts to misfire. Let’s look into more specifics:

Ignition System:

The Ignition System is responsible for the production and delivery of Spark. The Ignition System is usually the culprit behind most misfires.

The usual suspects (that cause a Misfire) are:

BAD ignition coil (remember, each coil firs spark to 2 cylinders).
BAD ignition coil cover.
BAD spark plugs.
Carbon tracks on the spark plug and spark plug boot.
Oil dripping (from the valve cover) onto the spark plugs and spark plug boots.

Testing all of the ignition system components is not hard and it doesn’t require expensive tools or expensive diagnostic equipment.

Fuel System:

The Fuel System is responsible for the delivery of fuel. If fuel is missing from any one specific engine cylinder, it will misfire.

Fuel system problems could include some of the following:

  1. BAD fuel injectors.
  2. Broken fuel injector connector (this is a very, very common problem).
  3. 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.
  4. BAD fuel injection computer not pulsing the fuel injector (this is a very rare condition, but it happens).
  5. BAD fuel pump.

Engine Mechanical Condition:

The pistons and valves are the ones that draw air into the engine. Usually all cylinders wear out evenly... but every now and then, either thru’ lack of maintenance or some mechanical problem, you’ll have one or more wear out at an accelerated pace.

To make the long story short, those cylinders (with accelerated wear and tear) to produce a less than average compression value that will cause a misfire condition.

Other issues, that can not be overlooked are vacuum leaks.

Now that you have an idea of what are some of the causes of a misfire condition... you might be asking yourself, ‘Where should I start?’.In this section, I’m gonna’ offer you a simple diagnostic strategy that should help you find and resolve the root cause of the misfire or ‘dead’ cylinder on your Quad-4 equipped GM vehicle.

STEP 1: Identify the dead cylinder.

This is the most important first test that will save you a lot of time and frustration down the road by narrowing down and focusing your misfire diagnostic.

Finding the dead cylinder usually entails connecting your scan tool to your vehicle and reading the misfire diagnostic trouble codes. Then by matching the misfire code to its engine cylinder using an illustration of the engine cylinders.

Now, the PCM doesn’t always set a specific cylinder misfire code. This is when knowing how to do and interpret a manual cylinder balance test comes in handy. In a nutshell, a manual cylinder balance test involves unplugging one injector at a time (to see which one has NO effect on the engine’s idle).

The fuel injector that does not worsen the engine’s idle when unplugged... tells you that that specific cylinder is ‘dead’.

STEP 2: Test the ignition system .

Once you have identified the dead cylinder, the next step is to check that all 4 spark plugs are getting spark.... since the majority of misfires are caused by a failed component in the ignition system. You should:
Perform a spark test (using a dedicated Spark Tester) on the spark plug wire of the cylinder that the misfire code is accusing of being dead.

Testing for spark with a spark tester is the most important first test... since you’ll know right away if the misfire is due to a lack of spark.

Check to see if the spark plug boots and spark plugs are swimming in engine oil from a leaking valve cover gasket.

If you got spark from your spark tester (from the cylinder the misfire code is accusing of misfiring), the next step is to remove the spark plug or spark plugs (of the affected cylinders) and check them for wear and tear, carbon tracks, anti-freeze, etc
If you get no spark, then the next step is to check for spark directly on the ignition coil pack tower.

You can find all of these ignition system tests here:
How to Test the Ignition Coils GM 2.4L Quad 4 (at:
Diagnosing a BAD Ignition Coil Quad 4 Case Study (at:

STEP 3: Test the fuel injectors. If the ignition system is not the cause of the misfire, then the next step is to check the fuel injectors.

You’ll need to:
Resistance test each of the 4 fuel injectors.
Do a noid light test of each one to make sure the PCM is pulsing them (activating them).
You can find the fuel injector tests here:

How to Test the Fuel Injectors (GM 2.4L Quad 4).

STEP 4: Test the compression of each engine cylinder. Other tests that should be done, if the ignition system and fuel injectors check out OK are:

Engine compression test.

Checking for vacuum leaks.

You can find the engine compression test here:

How to Test Engine Compression (GM 2.4L Quad 4).

The above list of steps may seem/sound like troubleshooting a Misfire is a complicated thing... but it really isn’t. Depending on your level of ‘wrenching’ experience, this is something that you can accomplish without taking it to the shop.

1 comment:

  1. This is a lot of work and unnecessary tools. Swap the coils, if the engine code changes to another cylinder = bad coil. Hold a screwdriver to the suspect cylinder's fuel injector and put your ear up to the plastic end - if you can't hear ticking = bad injector.