I've got a 2000 protege with the 1.8L that is running real rough and was throwing the code p0401 and p0300. I've since added new spark plugs and a new ignition coil in the car with very little change in how its running.

Does anyone have any idea what I might want to look at? I'm thinking the O2 sensor, but really any insite would be great.

thanks.

 

check the fuel filter may have a little water in it or something

 

if i am not mistaken, 0401 is limited or no signal from the second o2 sensor. i would check that.