well i just recently did a ls/vtec swap and after 2months of driving it it's throwing up 4 different codes..now i'm just wondering if anyone was having the same issues too...as of right now my car isn't tuned yet and it will be once it stops snowing here..if anyone has any advice or threoy as to what the cause can be it will be greatly appreciated..thanks...

1) PO420- Catalyst Efficiency Below Threshold (Bank 1)
2) PO450- EVAP Emission Control System Press Sensor Fault
3) PO453- EVAP Emission Control System Press Sensor High
4) PO505- Idle Control System Malfunction

 

-Do you have a catalytic converter?
-Did you run the vacuum lines correctly, and retain the sensor that sits on the top of your intake manifold (I guess that would depend on the type of head you are using).
-Is your IACV hooked up correctly?
-What trim level is the car the engine is in, and what ecu are you using?
-the answers to these questions will help me get an idea of whats going on. Thanks1

 

-yes i do have a catalytic converter
-the vacuum lines were all ran correctly the head is a obd1 b16.
-the IACV is also hooked up correctly.
-the car is a 4dr 96 LS and the ecu is a OBD2 P72

 

What harness are you using? The catalyst code could just be due to the converter being, well, old. I had a '98 RS that had this code, and it did not go away until I replaced the cat. Is your cat oem? Sorry for all of the questions, but its hard to correctly diagnose over the internet unless you have a lot of information IMO.