PO420 after replacing missfiring spider injector 4.3L

Question

i have just replaced the factory missfiring soider injector on my 01 chevy silverodo 4.3L
about 150 miles latter got code po420. i tested new injector before reinstalling the plenum no gas leeks. i did reuse old lower plenum gasget as it was in great shape. i have tested the plenum for air leeks none found. i do still have the factory spark plugs at 188000 miles could this be the problem? the truck is running better than it has in a very long time.any info will be very helpfull. thanks

Answer 1

I would replace the spark plugs, bad spark plugs can cause p0420

 

Possible causes

- Three way catalyst converter Bank 1

- Exhaust tube

- Intake air leaks

- Fuel injectors may be faulty

- Fuel injector leaks

- Spark plugs may be faulty

- Improper ignition timing

- Powertrain Control Module (PCM)

 

https://www.autocodes.com/p0420_chevrolet.html