extremely rough idle

Question

Idles so bad it feels and sounds like the muffler is about to fall off. The check engine light stays on, except at 45 mph-55mph it blinks.

Answer 1

Hi there

I would start with checking the plug wires and the ignition coil. The spark plugs can cause this issue as well. These are difficult plugs to access and may need replacing. The code P0300 means multiple cylinder misfires. This is why the engine is running so rough.

P0300 SUBARU - Random Cylinder Misfire Detected

Read more: https://www.autocodes.com/p0300_subaru.html