What Tests Can I Perform To Find The Cause Of The Misfire Condition?
The very first thing you'll need to do is identify the ‘dead’ cylinder and this is easily done by scanning for misfire codes (with a scan tool).
The most common misconception is that a scan tool will tell you exactly what to replace to solve a misfire code or codes. Reading the diagnostic trouble codes is only the beginning of your troubleshooting.
Once you have identified the cylinder that is misfiring (missing or dead), now you need to do some very specific tests to see what is causing the issue. Here's a break down of the tests that you'll need to perform on your 2.2L Cavalier (or Sunfire, Sonoma, S10 Pick Up):
Ignition System:
- Remember, identify the ‘dead’ cylinder first:
- P0301: Cylinder #1 Misfire. Cylinder #1 is the one closest to the drive belt (see photo).
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
- Check for spark using a spark tester. What you want to do is confirm that:
- All spark plug wires are sparking.
- Remove and physically check that none of the spark plugs are broken or are cracked.
If one spark plug wire or two are not sparking, then the next step is to see if that spark plug wire is bad or if the cause is due to a bad ignition coil pack or a bad ignition control module.
This is not as hard as it sounds. The following tutorial will show you how to do it in a step-by-step way:
- How To Test The GM 2.2L Ignition Coil Pack (at: easyautodiagnostics.com).
Fuel System:
Once you've checked and have confirmed that all four spark plug wires are good and sparking and that the spark plugs are OK, then next step is checking the fuel injectors and fuel pressure.
You should:
- Test all four fuel injector signals with a Noid light.
- Check the internal resistance of the fuel injectors.
- Check fuel pressure with a fuel pressure gauge.
You can find the fuel injector test tutorial here:
Engine Mechanical Condition:
By testing ‘engine mechanical condition’ I specifically mean checking that engine compression doesn't vary more than 15%.
- Test the engine compression of all engine cylinders.
- Check for vacuum leaks.
- This usually involves visually checking that the vacuum hoses are not broken, burned, or with dry-rot.
- You should also check for vacuum leaks by spraying carburetor spray around the intake manifold gasket area while the engine is running.
- IMPORTANT: When using carb. spray to check for vacuum leaks, the engine must NOT be hot or you run the risk of fire.
- Check that you don't have a blown head gasket.
You can find an engine compression test tutorial that explains how to do and interpret the compression test:
The following tutorial will help you test for a blown head gasket:
It seems like a long and complicated list doesn't it? What's gonna' make the whole process fast and easy is remembering that only one of three things is gonna' be missing (spark, fuel or air and by ‘air’ I mean engine compression).
If you're getting the impression that you CAN find out the exact cause of your misfire condition on your GM 2.2L car or pickup (Chevrolet: Cavalier, S10 Pick Up, Pontiac Sunfire, GMC Sonoma), you're right! Let's turn the page and find out more.
