PO300 - Nissan Misfire Problem

Question

My manual transmission car has been misfiring on multiple cylinders and has gotten progressive worse to where it surges when driving it. I had the catalytic convert and O2 sensors replaced by a mechanic and have taken it back numerous times and he can't figure out what is wrong. I bought a Pocket Scanner and it reflects a PO300 error which reads misfire fuel comp catlyst evap O2 sensor O2 heater. Could the Catalytic converter be causing the problem? What other things could be causing the problem?

Answer 1

I would check for intake leaks and also do a compression test first 

and try to disconnect each injector while the car is running to see if there is an RPM change, also check to see if the spark plugs and coil are good 

if everything is fine, I would switch to using 91 octane fuel and use a good fuel system cleaner (maybe do an intake flush also)

 

fuel pressure should be 51 psi at idle (if a lot lower or higher the fuel pump might be bad)

you can also try to clean the mass air flow sensor with mass air flow sensor cleaner

a bad catalytic converter can also cause a p0300