I had the P0303 and P0300 code come on some time ago, noticed it had not had new plugs so I changed them. Well the P0300 has not come back, but P0303 tripped the other day. It has only happened on really cold starts with it being cold outside, i.e. in the morning. I did not know if there was a correlation, and I did not see anybody else from the search function have it trip at idle. Any ideas? I am going to try replacing the plug wires.