Okay guys I'm new to this and new DIY but hey there's only one way to learn right. Anyways I have code p103 p200,p300,and p400 from my dash trick thing. The engine light is not on and every time they hook up a scanner to my car no codes come up. So every 2-3 days I have a misfire and all but one time it happens when starting the car that one time was at a red light. Also not sure if related or not but the last two times I put fuel injector cleaner in my gas tank the car actually shuts off and takes multiple times to start the car.
Ford focus 2003 spi SOHC LX
What I done: fuel filter, air filter, spark plugs and wires, pcv valve, and two small vacuum lines that connect to two nipples on the firewall.