P0300 = Random multiple misfires. Can be caused by a lot of things, usually not plugs/wires though, those will set a code for the particular plug or wire that is bad. It is caused by something that controls all the cylinders. Bad coil, MAF sensor out of range, O2 sensors reporting incorrect data, even something like an exhaust leak at the manifold can cause it.
Run a fuel pressure test to see if you have low pressure. Should have 55-62 psi.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Check for a vacuum leak.
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
If you have access to a scan tool that will read live data check the fuel trim numbers both short and long term, and the O2 sensor response.
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Tuesday, January 10th, 2017 AT 5:12 PM