2010 Liberty P0300, P0152, exhaust leak **HELP**

[Gunner0306]

So I recently picked up this 2010 Liberty, I new it had a few issues but not this serious. Currently I have codes P0300 and P0152, also I know the vehicle has exhaust leaks at both CAT's (appears new ones were welded in very poorly). I have replaced plugs and ignition coils, no doubt I have a misfire on cylinder 3 but I'm unsure of how to trouble shot and solve the problem.
Vehicle will start but it's rough, it wont idle on its own, but can be kept running by feathering the throttle. I have a scan tool from amazon and have pulled/cleared the codes mutiple times, the OBD scanner has a live data feature but I honestly dont really know how to use the information. I'm going to attemp to attach pictures.

Forgot to add I have removed the vaccuum hose from the brake booster and could not identify and leaks

ANY HELP IS GREATLY APPRECIATED!!!!!!

 

[eagle1one]

Your P0152 is an Oxygen sensor defective. It controls the fuel injectors on that side of the engine through the computer. You have two banks, Bank 1 & Bank 2 and you have 4 O2 sensor which are the same part# Hope this helps!

 

[Gunner0306]

Thanks for the info ended up pulling the exhaust and fixing all the leaks, replaced all O2s, pulled the valve cover to confirm it didn't loose a rocker arm, and then ran a head gasket test followed by a compression test. Zero compression on cylinder 3 so I assume it cracked a valve seat.

Looks like I'll be pulling heads.

 

[eagle1one]

Your P0152 is an Oxygen sensor defective. It controls the fuel injectors on that side of the engine through the computer. You have two banks, Bank 1 & Bank 2 and you have 4 O2 sensor which are the same part# Hope this helps!

Also I changed one on the passenger side catalytic ( one before the perverter and one after the perverter) on the perverter closer to the exhaust manifold is the one I changed. It controled the injectors on the passenger side
You can check this out by unplugging the injectors one by one and watch your engine vibration. If there is no difference between plug and unplug means the cylinder is not firing . so the injector is not opening due to the O2 sensor
I am 72 years young and did all this with the help of my son trade school graduate in automotive mechanic.
Need any more help ask an I will help .