Power loss

Hey guys,

So I recently had been having power loss when accelerating up to freeway speed along with taking off from a dead stop on hills. I replaced my front pipe and front O2 sensor finally due to a P0420 CEL. New plugs and wires were installed within the last 200 miles, I checked the coil and knock sensor as well and those checked out ok. Any ideas what else I should check? Secondary cat? How do I check the O2 sensors to make sure they're good?
Thanks.

Anyone have any thoughts on what else I should be checking? Thanks.

The second cat can be checked by disconnecting it from the manifold and midpipe then visually inspecting it for obstructions. Also have you let your car run low on fuel lately ?? are the wires seated properly on the plugs/coil pack leads?

Originally Posted by GEE-OTTO

The second cat can be checked by disconnecting it from the manifold and midpipe then visually inspecting it for obstructions. Also have you let your car run low on fuel lately ?? are the wires seated properly on the plugs/coil pack leads?

I'm waiting on my new gaskets to get here then I'll check the 2nd cat. Lowest my tank ever gets is to 1/8th of a tank. I'll have to check the plugs again, I'm pretty sure they're in there securely, I've has the boot pop loose before and tend to check anytime I'm under the hood.

I'm starting to wonder if I have a defective upstream O2 and if I should replace booth since I only replaced one of them.
Thanks for the input Gee!