Hey guys im new to this forum and i cant post on troubleshooting so i need help. a while back i got a p0420 code and it came on and i deleted it and it never came back. so recently i got my spark plugs, ignition coils, and wires replaced at 45k and yes i know thats bad and i dont believe they were replaced before because i bought the car at 23k miles. as soon as i replaced these i got a major loss in power and a little hesistation came up today. i believe its either cat or compression loss. let me know what you guys think

 

P0420: Catalytic converter below efficiency threshhold.


That only pops if your cat has a hole in it, ie, damaged.

 

If you got a major loss of power after changing the ignition, check that you didn't plug something in incorrectly. That would be step 1.

 

^+1
Check to see if the wires snapped on tightly onto the coils, it happens.
It could also be possible that a chunk of catalytic converter broke loose and is clogging your exhaust.
With that code your cat is likely bad and can ruin your engine if you continue to drive it.
Drop it and inspect ASAP.
If it's clogged take the sensor out and gut it until you can replace it with a new one, or a midpipe (my choice), or park it.
If it's broken up and the back half of the cat is still intact that's a good thing, if the back half is broken up you'll have to take the rest of the exhaust off and try to shake out any remaining pieces of the strata that may be in there.