Check engine on, code PO300?

Hi,

A P0300 can be caused by several things. For example, worn spark plugs, low compression, worn ignition cables, fuel pressure issues, engine vacuum leaks, and so on.

Have you checked for vacuum leaks? That is the most common cause. Also, does the engine run rough specifically at idle and in gear?

Let's start with checking for a leak.

Here is a link that explains how it is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, let me know when the last tune-up was done and if you have already checked fuel pressure and engine compression. Additionally, let me know if this is the original engine.

Take care,

Joe