Infinity QX4 After-fire

[mwatson1445]

I have a 2001 Infinity QX4 that blew a head Gasket. I swapped out the engine because the old engine had 250K miles on it. Car starts fine but I get an after fire in the Catalytic converter on the Passenger side Tried swapping the Cat problem always stays on the Passenger side. Tried disconnecting the Mass Airflow Sensor No help. Car runs very poorly and the Catalytic gets Red Hot. Car runs poorly. Not sure how to adjust timing if that is the issue because the car is all computerized.... Changed the ignition coils and no help... Any ideas?

[Towncivilian]

Your cat is clogged, replace it to begin with.

Welcome to NICO.

[zach7685]

I second that cat comment im amazed it turns on...

[ferrariowner123]

What they said.
-Kyle