05 Sunfire reading P0420 after misfire issue

dimevision

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Vehicle started misfiring Oct 6th and was resolved Oct 10th by replacing Ignition Coil and Ignition Control Module, as well as Spark Plugs, Plug boots, fuel filter. Then Oct 14th while driving the car felt as it was "heavy" feeling or lack in power, after a few miles it stopped. The Service (wrench) light came on and wouldn't start though it would crank. On third try it started but stopped after about 100-200 ft of driving. The Service light is off and now the check engine light is on, used an OBD-II reader on it and it read P0420. I need some help determining on what is wrong so i can fix it, im trying to avoid mechanic shops. I can't tell whether the cat converter is bad or not, theres no sulfur "rotten egg" smell. Any help would be appreciated.
 
Did you replace the "distributor cap" or coil mounting bracket?

dosent have either of those, it all sits on top of the engine

2003.pontiac.sunfire.20167342-E.jpg
 
How does the spark get from the coils to ths plug boots?
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I did a google search on P0420 and came up with this pointing to converter or air leak before converter

"It doesn't take long for even somebody not in the industry to find out how
a P0420 is set. It is set when the catalytic converter fails the ECM's cat
efficiency test.

The test is, from my readings, this: The ECM commands rich for 5 seconds to
drain the cat of oxygen. Then it commands lean for five seconds, measuring
how long it takes for the secondary sensor to start flip-flopping. If the
rear sensor flip-flops too soon, the ECM assumes the cat's unable to store
sufficient oxygen, and sets the P0420.

I also understand that there are certain unusual circumstances that can
lead to a P0420 even when the cat's fine. These would include air leaks
into the exhaust after the primary sensor, or before the secondary. Also,
certain Honda models (I know the OP's car is a Toyota) have problems with
the igniter electrical connections that can lead to a false P0420"
 
if its a catalyst low efficiency code you need a catalytic converter. chances are when it was miss firing it was pretty bad and raw fuel was getting to the cat. not good. check for exhaust leaks first the replace the cat.
 
@Zimgxp
the coil, boots, and module is that big black rectangular thing that sits on top of the engine as seen in the pic(the thing with the 4 bolts next to the oil cap) its all one bundle.

@melsg5 & white98bonn
Ill be getting a new cat pretty soon shipped to O'Reilly's, not a universal one though, so yeah i ruled out alot of stuff and as white98bonn said it most likely the cat converter, so thanks to everyone who gave suggestions, ill keep it posted if it fixed it or not.
 
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