i have a 2003 3.5 with a random/multiple misfire code p0300

also has codes p0420 and p0430 for catalyst below threshold bank 1 and 2

the guy i got it from said he did a tune up about a year ago

any advice please help thank you

 

Are you actually having noticeable drive-ability issues? or just an SES light?

Did he have documentation on the plugs used? I would check to see if they are NGKs first.

Pull up the Factory Service Manual (FSM) and do some searching here on the org. I am sure you will find very good information on the subject since you are definitely not the first to have this problem.

your Catalyst codes likely mean its time to gut/direct replace/upgrade some exhaust components. You can also find good info on the org regarding this as well. Good Luck!

 

http://www.nicoclub.com/FSM/Maxima/

 

No i didn't ask what kind of plugs
Yes it feels like a misfire and my 97 feels like it has more power
my cluster needs to be replaced so SES does not light up
and do you think the codes are related
thanks for your help