Misfire code

Welcome to 2CarPros.

As far as the codes, what one is coming up for the catalytic converter? Is it a P0420? Also, considering the mileage and the two cylinders are next to each other, we may have an issue with a head gasket. You will need to check engine compression to confirm it is within spec. Also, I need you to check for a head gasket issue.

First, here is a link that explains how to check for a bad head gasket:

https://www.2carpros.com/articles/head-gasket-blown-test

Here are links that discuss engine compression, causes for low compression and how to check compression:

https://www.2carpros.com/articles/symptoms-of-low-compression

https://www.2carpros.com/articles/the-reasons-for-low-compression

https://www.2carpros.com/articles/how-to-test-engine-compression

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Here are the directions specific to your vehicle for testing compression. In the directions, it says to disconnect the ignition module. I attached a picture of its location.

Engine Compression Test

Perform the following steps to conduct a compression test.
1. Conduct the following steps to check cylinder compression.
1. Engine should be at room temperature.
2. Disconnect wiring from the ignition module.
3. Remove the spark plugs.
4. Throttle body valve should be wide open.
5. Battery should be at or near full charge.
2. For each cylinder, crank engine through 4 compression strokes.
3. The lowest reading cylinder should not be less than 70 percent of the highest.
4. No cylinder reading should be less than 689 kPa (100 psi).

Important: The results of a compression test will fall into the following categories:
Normal. Compression builds up quickly and evenly to specified compression on each cylinder.
Piston Rings. Compression is low on the first stroke, tends to build up on following strokes, but does not reach normal. Compression improves considerably with the addition of oil.
Valves. Compression is low on the first stroke, does not tend to build up on the following strokes, and does not improve much with the addition of oil. Use approximately 3 squirts from a plunger-type oiler.

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Let me know what you find or if you have other questions.

Take care,
Joe

Happy to help. Listen, if the converter has failed and is plugged, you will experience power loss and most likely a misfire. The extra back pressure can cause engine damage, so keep that in mind.

Feel free to let me know if you have other questions or need help with anything. I will watch for your reply on what is found.

Take care,
Joe

Welcome back:

That code indicates the catalytic converter is operating below threshold. With that code, 99% of the time, the converter needs replaced. If it is causing issues with back pressure, it may be the source of the problem. However, I would strongly recommend checking for head gasket issues.

If you get the chance to check for head gasket issues, let me know what is found. Also, let me know what compression is found. With that, I will be better able to direct you. However, the converter will most likely need replaced.

I will watch for your reply. Also, let me know if you have other questions.

Take care,
Joe

Welcome back:

You will need a compression gauge. Most parts stores will lend you one. As far as the gasket, they get old and fail. It doesn't need to be overheated.

Let me know if I can help.

Take care,
Joe

That's not good. Have you tried a salvage yard? Also, are there any u-pull it salvage yards near you? There are several near me and I know there are many 2.2L GM engines. I'm sure if there is a place where they allow you to remove the parts from the salvage vehicles, you could find one.

Let me know.

Joe

Wow! That was such a popular engine. I just went to a nationally recognized parts store web page and looked up the o-ring. I'm not to use company names here, but the initials of the store are A Z. Take a look at the attached picture. The picture is for a 2005 cobalt 2.2L.
Do any of those look like what was removed?

Let me know.

Joe