I have a 2006 F-150 with the 5.4 ff and it has 88,000 miles. I had the plugs changed 3 weeks ago after my check engine light came on and the code was catalytic efficiency below threshold bank 2, knowing they needed to be changed soon but doubtful it would fix the problem. Afterwards I was getting same code and cylinder 6 misfire, so I changed #6 coil and it made it worse. truck went from skipping for about 1/4 mile before clearing up to about 2 miles. Afraid I was gonna break down I finally took it to a shop. They said we need to change plugs and #6 coil and I told them that was already done. So mechanic said probably the injector, and he changed the injector and that helped a lot but still missing. Come to find out that injector was bad and my coil was good and parts store gave me coil for 4.6 instead of 5.4, that's why it ran worse after changing coil. Truck runs good now but catalytic efficiency below threshold on bank 2 is still coming back up after clearing codes. People kept saying a o2 sensor bad so I swapped the sensors from driver side to passenger side thinking if that's the case it would now say bank 1, but its still reading bank 2. Any advice on what to do next to solve this problem?

 

Prob have bad cat. If the injector on cylinder six was bad prob melted the cat down inside. You could always give it a tap with rubber mallet see if it rattles. Remonve sensor in the middle and inspect to see if its broken. Another thing if you can watch data stream watch both O2sensors on bank to if downstream one is cycling like upstream one then your cat is shot.

 

A low ment the back O2, has a bad heater circuit. Was it Sensor 1 or 2. Your Code reader will tell you that in the freeze frames. I would double check which one it is before deciding to replace catz. If you flipped the 1st ones it wouldn't change the code. You flipped the wrong 2. Amazing you got them out that easy. The back 2 on the banks are different than the front 2 with different part numbers. Navigate your code reader and open the diagnostics it offers. There is a lot of info you may not know yet there for you. Make sure to document it all. Too much for you to remember.

 

Is the code P0420 or P0430? If so, I've run into this problem with a lot of different cars and trucks. I always perform a fuel system service before I try diagnosing it as this is a common problem, and this usually fixes it. I've only ever used BG's fuel system service so I don't know how well other products work.

 

FSM I"m not sure what this means can someone maybe break it down a little more?

 

It is code p0430, I've ran lucas injector cleaner in it and the shop supposedly cleaned the fuel rail when they replaced injector but no idea what they used. I've heard of BG's before. Where can i find this product at?

When I swapped the o2 sensors i did the 2 on the bottom. Driver side top was easy to get to but passenger plug was unreachable without disconnecting exhaust completely. The code reader is not saying anything about o2 sensors that's just what parts store told me but I don't think that's the problem. The shop told me once they replaced injector that would fix it but again it did not so I'm gonna pay them a visit today.

 

Code 0430 means bank 2 catz is bad, the o2 sensor between it and the muffler is bad. With a good code reader you can navigate the pages it offers and document your codes, speed frame data and I/m test data. It will also help you and point you into a better dirrection of repair. Again, look to your I/M test data. Things that are (OK )have passed the test, Things incomplete havent and are still suspect of being faulty. Every thing in the Emissions section has to (OK), or not be there at all. It is usually best to do both catz and O2's. Usually the exhaust is in rather decrepit shape anyway and duals after the muffler are also added. Also listen for the sound of the exhaust leaking. It can cause you fits. Many times the catalytic muffler downstream of the leaking fuel injector gets fried because it gets too hot. Doing the exhaust and O2's at the same time perty much takes care of exhaust problems, if motor tests OK. Damaged, clogged catz/exhaust caused fits of back pressure unless it leaks out. Many times on inspection you find a split in the exhaust somewhere. / That's age and not the cure, just part of the repair. There is another O2 removal tool that is shorter and works 90 degree better and closer. Remember some of these Catz are like filled with micron sheets of glass like material. Easily damaged by just being rough with them.

 

Some scan tools have the availability to monitor certain sensors your oxygen sensor in the front will cycle up and down always changing between rich and lean the back oxygen sensor should stay at steady voltage monitoring the efficiency of the cat. If the second oxygen sensor is cycling like the front then it is no longer any good. But you need to be able to monitor voltages.

 

Harbor Freight has a very inexpensive code reader that can really help you.

 

I have an actron handheld one but it does not give individual sensor readings, just I guess you'd say a general area to start. The shop I went back to put it on there diagnostic for free and the #1 sensor on both side alternated between rich and lean(which they said it should) and #2 between 1.48&1.65 volts I believe(which the mechanic said was good too), but the guy behind desk says they are used so will not give accurate reading. He could change all 4 o2 sensors for $320 plus labor (which means $80 a piece for o2 sensor but I already have 2 that I paid $41 a piece for) then he says if that don't work we will replace converters for $1000 plus labor.