Code PO303, cylinder three misfire

Hi,

Since it stays on cylinder three and you notice it at idle, chances are it could be low compression on that cylinder. You did confirm there is spark to cylinder three and an injector pulse, correct? Also, just to confirm, you only notice it at an idle, correct? What is likely happening is as the RPMs increase, the misfire is still present but not as noticeable.

Based on the miles and what has already been done, that is what I would recommend checking next. You have already tried all the electrical components. If it was a random misfire and not specific, then I would think it could be something different.

Here is a link that explains how to test engine compression. You will need a compression gauge, but most parts stores will lend one to you free of charge.

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

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

Take care,

Joe