Rhino8123

I have a 2014 F150 5.0L with 165k miles on it. When I bought the truck used it had a P0430 on it, but ran fine. The previous owner had straight piped the truck and then had a crappy muffler welded back in at some point. The only option was to have a muffler shop weld in a new cat on the driver side as the entire system was welded and no longer bolt on or re-do the entire exhaust system. I ended up redoing the entire exhaust system as I figured it'd be easier to maintain in the future.

Both catalytic converters were replaced with Magnaflow direct fit cats. All 4 O2 sensors were replaced with Motorcraft sensors. I installed a walker SS Quietflow cat back system (resonator, pipe, muffler, and tailpipe). Now the entire system is bolt on using the factory mounting points.

My P0430 came back within 2-3 drive cycles. I cleared it and it did the same thing again. I contacted Magnaflow and they recommended giving it 250 miles to see if the cat would "break in". This also did not clear the code. I dropped it off at the dealership and explained all the new parts and what Magnaflow had recommended. The tech ran diag on it and did a KAM reset. He performed the drive cycles and the P0430 came back. He recommended replacing the cat again. I did a warranty swap on the driver side cat, and I'm still getting the same results. The P0430 continues to return. I'm now also getting a P0420. The only codes present are P0430 and P0420. The truck still runs and idles fine. There is no rotten egg smell or anything from the exhaust. I do notice on cold start that it smells like it may be dumping gas, but that goes away pretty quickly. When I first got the truck with about 140K on it, I swapped all the plugs for Motorcraft plugs. I've replaced the PCV valve, air filter, cleaned the MAF, a bottle of Techron (enough for my 36G tank), fresh oil, and a Motorcraft oil filter. I had an oil leak fixed and the tech noted that the heads had sludge in them while he had the valve covers off. I've been running very short oil changes to try to clean the sludge as best as possible. I have also checked the exhaust system for leaks using a shop vac and soapy water. I didn't find any leaks (although it's difficult to see the entire exhaust manifold on either side).

I'm not really sure at this point if I truly have a system problem or if the aftermarket cats just aren't efficient enough as Ford wants. Am I missing something, or are Magnaflow cats just not good enough?

Siber Express

You might try an O2 Sensor Spacer, they back the sensor out of the exhaust a little and it lets it fool them into thinking they are working. My friend had to do that with the Walker EPA Compliant converters on his F150

stars_fan

I second the defoulers in the rear O2

Rhino8123

At this point, I think that's what I'm going to do. I was just really trying to figure out if I have a different issue or if it's just the fact that aftermarket cats aren't as good as OEM cats.

Leandro Lopez III

on my 2018 3.5 Eco. I paid a shop to weld these on mine. I made the mistake of cutting them out to make the exhaust sound meaner. I regretted it but had sold my OEM cats. Got these replacements and didnt have issues.

stars_fan

You can download forscan and do the mode 6 test. You’re looking for catalyst efficiency and that will tell you how far off thing are in the computer.

Rhino8123

I have Forscan, but obviously don't know how to fully use it. I appreciate that. I'll give the mode 6 test a try and see if I can figure anything out.