Low or no power, changed the mass air flow sensor? OBD showed a problem on left side cat converter? Runs good one day and bad the next. Problem started after hurricane. Acts like exhaust is plugged up. Changed fuel filter and plugs and wire, cannot find air leaks. I stepped on gas peddle and pump peddle and problem was gone and i drove it to car repair while it was running good. I parked it and the next day the repair man start the car and had the same problem. HE changed the map sensor car was ok until I started it the next day.

Check intake manifold vacuum with a vacuum gauge. Should be 17-21 inches. Low vacuum 10-15 inches would indicate a bad cat. Or you can remove the oxygen sensor and drive it. If the power is better you have a bad cat. Misfires can melt the cat converter.

The O2 sensor (2 on V engines) are in the exhaust system pipes before the catalytic converter, the next sensor is the efficiency monitor for the catalytic converter system it looks like a O2 sensor but performs a much different function as far as testing goes. The codes you have follow.

P0420 - Catalyst System Efficiency Below Threshold Bank 1
What does this mean? In most cases it means the catalytic converter is worn out and that is sensed by the catalyst monitor I spoke of earlier.

P0102 - Mass or Volume Air Flow Circuit Low Input
Faulty mass air flow sensor
- Dirty mass air flow sensor (located in the air intake hose to the engine from the air cleaner)
- Dirty air filter
- Mass air flow sensor harness is open or shorted
- Mass air flow sensor electrical circuit poor connection
- Intake air leaks

Now if your old fuel pump was loosing pressure it tends to lean out Overheating your catalytic converter and melting it so exhaust gasses can't flow To test this is easy just remove the two bolts holding it on the engine pipe Start the engine if runs fine replace cat converter

Common Problems That Trigger the P0152 Code

• Defective Oxygen Sensor
• Faulty Oxygen Sensor wiring or connections
• Shorted Oxygen Sensor Heater element(s)

Common Misdiagnoses

• Oxygen Sensor is replaced when the problem is faulty Oxygen Sensor wiring or connections
• Oxygen Sensor is replaced when the problem is an over-reporting Mass Air Flow Sensor, clean mass air flow sensor first, to see if thats the problem. good-day ! just type this in search on pc. 02 sensor symtoms, and it will give you the details of a bad sensor.

First the converter should not have failed until
it was at least 12 years old

The cause of the failure had to be corrected first

The front 2 --O2 Sensors get changed at 100,000
miles or before if they fail

When someone says they changed something,
I take that as meaning, you did it yourself without
any system knowledge or testing,thus you still have issues

no-- but could mean that the O2 sensor is not correct
it is a common misconception that all of the oxygen sensor are the same
the fact is that even they are known a oxygen sensors there are 2 completely different units
the sensor in the exhaust manifold before the cat converter is in fact a heated oxygen sensor and it's function is to report the exhaust composition so that the ecm can adjust the air/fuel mixture
the other is an o2 sensor located after the cat converter and fine tunes the system after the cat converter has done it's job
if the cat converter is faulty , the o2 sensor will try to have the ECM correct the mixture
the loss of power if it is a cat converter comes from a blocked exhaust system and that is most evident at high rpms or under power

I had the same problem but when I changed the Mass Air Flow it was solved. I am suprised that you changed the MAF and you are still getting problems. Please get an OBD check. The problem must be having something to do with electronics and the ODB will definetly be able to read it.

Brake loose connection between cat and exhaust manifold , it will allow exhaust gas to go out before cat , and see if it's restore the power on the engine.
If it does then your cat is clogged.
If not it's also might be Throttle Position Sensor , or Mass Air Flow Sensor.
You can't remove cat , you have to replace it if it's bad. Cat is a part of Emission control system.

Cat is usually damaged from vehicle misfiring, Those codes you posted are a MAF, idle control, and 02 sensor codes. The MAF sensor could be reading incorectly causing the car to run rich or lean, and giving the 02 sensors bad readings, i would deffinetly look into the MASS Air Flow sensor, which is located on the intake tuping near the airbox

You can also try cleaning it with MAF sensor cleaner

An O2 sensor will not cause a miss, period. I would think the problem may lie with the #3 coil, or the wiring to it. What are the trouble code(s), give me those and I can be more helpful