Just bought my daughter an 03 protege3 103,000 miles .. engine light came on says code p0303 miss fire # 3 cylinder . So changed all plugs,still on , changed plug wires ,still on , changed coil pack disconnected batt, went off for 2 days now back on ... when engine light on all time car not missing, when engine light flashing car starts missing , what next check all vacumn hoses and seals?

 

"what next check all vacuum hoses and seals? "

Yes, indeed.

A flashing CEL means the catalytic converter could be damaged if you continue to run the engine.
Check the air intake hose. It may be cracked and lean out the air fuel ratio intermittently.
Check the fuel pressure and the fuel injectors. At least put a good fuel system cleaner in the tank. I am thinking Techron.
Clean the EGR system.

 

how do you clean the EGR?

 

Vinper: watch Youtubes on "how to clean an EGR System". It does not have to be brand specific.

 

ok thanks,,