A misfire can be caused by several different things. Usually, however, it is something simple. Have you checked for engine vacuum leaks? Are there any codes stored other than the random misfire (P0300)?
If you haven't checked for leaks, take a look through this link. It explains how to do it.
Also, if it is a specific cylinder that is creating the misfire, it could be lower on compression. That can cause a random misfire and rough idle.
Let me know if there are other codes or if it is specifically a P0300.
Also, if there are no vacuum leaks and no other codes, I would suggest checking engine compression and fuel pressure. Here are two links that explain how it's done:
Let me know as much as you can. For example, is there an odd odor from the exhaust, do you ever notice smoke from the exhaust, is the engine using coolant, and so on.
Tuesday, September 7th, 2021 AT 8:12 PM