Chevy Cavalier

[llmensa]

I have a 2000 2.2 the computer will set a PO420 code that says it's catalyst system efficiency below threshold (bank 1) installed a new upstream (o2) sensor cleared codes and it comes on again with PO420 code any help!!

[Classicrocjunkie]

Does your exhaust smell like rotten eggs? You might need a new cat

[noshun]

Originally Posted by Classicrocjunkie

Does your exhaust smell like rotten eggs? You might need a new cat

If it does this is fuel getting into your cat and breaking the Platinum and Rhodium that are sprayed onto the mesh. This could be that you aren't burning all of ytour fuel and there is too much o2 in the exhaust gasses hence the light and code. Change you plugs and leads! That's more than likely the problem if not the coils, igntion system or crank pos sensor but probably just plugs and leads!

[Classicrocjunkie]

If the computer is dumping all that extra fuel in there plugs and wires are going to do too much more... prolly still run rich... but start with your O2 sensor..wouldn't hurt to do both at once.

[noshun]

Originally Posted by Classicrocjunkie

If the computer is dumping all that extra fuel in there plugs and wires are going to do too much more... prolly still run rich... but start with your O2 sensor..wouldn't hurt to do both at once.

New Motor!!!