I’m going to attach some photos of my O2 sensor pids. Upper is bank 1 sensor 2 lower is bank 2 sensor 2. The dips are far different but both at .75 volts. So here’s from the beginning. back in November, I started getting a misfire on cylinder eight then after getting that misfire, I had to keep driving the vehicle for a couple thousand miles as the misfire was only at idle. Did a down test and realize that I had a misfire on cylinder eight due to compression loss from the intake valve. So as I was driving a couple thousand miles before doing the repair, I wound up with the PO 430 which I assumed was from fuel dumping into the cylinder into the cats at idle not being burned. after receiving that code, I rebuild the engine when I rebuilt. I put new heads oil pump pick up tube oil pan chains phasers cams the whole 9 yards. The only thing left was pistons is what I did not touch. Replace the catalytic converters both sides still remain with a PO 430. replace them two more times but wound up with 420s and 430s but I did use cheap cats. I put my next set of cats on and now back to a PO 430. I have no clue what’s causing it. I have clean the throttlebody the mass airflow sensor did a tuneup, cool packs and plugs. I’m not sure what else to look at. Flex fuel is below 10% for the most part. I do have had a rough idol since the rebuild which I also had before, but it was due to compression loss now I cannot figure out the rough idol sometimes when stopping it even but very, very rarely. I have cleaned the throttlebody trying to counteract it , and put two different sets of motor plugs and now a set of NGK iridium plugs. I put on Saturday and still receiving a PO 430. Below is my 02 sensor charts from today. I’m a ford tech so have access to anything you need comp wise but cannot figure this out. The rough idle is very noticeable. And obviously the CeL for the 430. Any ideas?

 

You need instead to graph S1 vs S2 for both banks. That will give useful information. You'd think a "ford tech" would know that....

 

I just came from GM. Very new to ford. Only about three weeks so I’m not familiar with them or the comp systems yet

 

I should also mention upstream are new and the one downstream. The one with high fluctuations is only old one.

LT trim bank one is 6.45%
LT bank 2 is .78%
and shorts are both around 1%

 

Age of parts doesn't matter (much).

Do the graph as I suggested so the ratio of switches can be observed.

You also need to identify engine and model year.

 

crap sorry. I had it in the first one and it deleted I had to retype it all. I’ll post the graphs tomorrow. Do you know what it’s called? I’ll be using IDS. 2014 F150 5.0 coyote

 

I’m not a tech but did you say anything about injectors? Fuel system pressure test? Stuck or junky injector or injector wires?

 

ik going to try a pressure test today. One injector is old and I had a code for it but it went away after rebuild and never came back. Number 8 is an aftermarket. No smoke at startup or fuel smell. No codes or misfires either

 

Since you're using "cheap cats" look at them first regardless of how many times you replaced them. If they're cheap cats, that's probably how they will behave.

Your most expedient action would be to install anti-foulers on the downstream O2 sensors to back them out of the exhaust stream. One per sensor usually does the job, extreme cases may require stacking a second one in there. You can buy ready-to-install ones on eBay or you can buy ones at your local parts store and drill out the base so the sensor's element will fit through it.

 

I done that for awhile and it worked. I now have the 400 cell magnaflows which I don’t thing is cheap. Close to foctory price. I tried cheap on the middle because I was tired of replacing them. The 420 is gone with the magnaflows but keep popping a 430 even with a ford one