I got the P0300 and P0301 engine codes on my 2003 Nissan Altima Sedan

Question

2003 Nissan Altima 3.5. Code read P0301 , which is #1 cylinder misfiring. So we checked for air leaks and we get nothing. We changed all spark plugs intake gasket and #1 coil. Get everything back together for all resetting procedures and test drive. Car turns out to be extremely worse. Scan iht again. NOW it reads P0300. We triple checked all connections, and we took Tha intake back off made sure all coils and spark plugs were okay. Once again get everything on, test drive i
It. Car still stumbles in high RPM

Answer 1

what type of fuel are you using? low octane fuel can cause this issue, you 91 octane from shell and use a good fuel system cleaner

I would clean the mass air flow sensor with mass air flow sensor cleaner, also try an intake flush like sea foam to clean the intake valves.

Problem might also be a air to fuel ratio sensor sensor 1 on bank 1 and 2
if still nothing I would also check fuel pressure it should be around 51 psi at idle

 

if you need the compression specs, see below