Its a 2006 f150 fx4 5.4 3v. I have a high flow cat gone bad. It sounds like something broke off inside of it. Trying to figure out what caused it to go bad tho. I had them installed in december with new plugs, COPs, and fuel filter. Ran great till about a week ago. Now its lost top end power and you can hear it rattling. Ordered a new one just waiting for it to get here.

Im getting misfires in cylinder 5 and 2. Would a bad cat cause the misfires? Their not throwing a code either.

Lastly, would a bad o2 sensor possibly cause the cat to go bad this quickly? And if so, would i be ok swapping the front o2s to the rear and putting new ones in the front, or since its probably just the bank2 rear o2 should i only replace that one?

 

I think the misfires would cause the cat to go bad and not the other way around. That is how my stock cat got clogged and started throwing codes. The o2 sensor should not affect the cat either, unless it was telling the computer to dump too much fuel and you were running rich. I would take care of the misfire, before I replaced the cat again.

 

There has to be a reason why the cat went bad, either from the engine running to rich or too lean or by installing them improperly.

 

Well ive been running a gryphon monochrome since the exhaust was installed. no air intake so i dont need a custom tune. Im gonna go through the plugs, cops, and injectors this weekend before i replace the cat. I am also thinking about changing the o2 sensor on bank2 rear.

if im getting misfires was is the engine light not coming on? i would never know i was getting them if the cat was clogged cause it runs great other then that

 

I felt my misfires. They were a hesitation, then a backfire, going up the freeway onramp. The backfires were what ruined my stock cat, I'm pretty sure. Mine did not throw any codes for that, either. New plugs, front o2 sensors, fuel filter and cleaning the MAF helped mine out quite a bit. No more misfires.

Good luck

 

you replaced the front o2 sensors? i read on here somewhere to replace the fronts, and move the fronts to the rear. also i dont feel my misfires anymore. i had them bad before i changed the COPs and now the truck feels great it just bogs down and ive lost top end power. i just cleaned the MAF and TB last weekend.

 

Yeah, I bought new front o2 sensors and left the old ones in the rear, behind the high-flow cats. My drivers side front o2 was baked. It had black powdery carbon crap all over it.

 

alright. ill check the front ones then. i thought i read it was the back ones that always went bad. but ill check all of them.

 

good luck hope you find the cause....

 

Any word on this?

I just had the Dealership check out the truck for a sputtering/stumbling issue and they told me I had a bad miss in #4....Coils were good, so new plugs went in and the truck still felt like it was bogged down so now they tell me my Hi Flow Magnaflow cats are clogged up and gone bad No rattling though (I've only had them for 5months)

Do you think this is really the problem? Should I jsut pull the cats out all together and have teh o2's turned off with my tuner? (NO FL Emissions)

 

If you're using an sct programmer you can turn the rears off through the menu.....

 

I realize that.......Yours saying I should just pull the cats off all together instead of trying to replace them?

 

Your misfire is contributing to a rich factor which eats away the catalyst and prevents it from filtering gases thus clogging up and blocking flow, choking the bank that it is running on. Once fixed, you shouldn't have another problem.

Man these 2006s seem to like having misfires it appears, this is about the 4th one I recall reading had a misfire and 1 destroyed cat.

I would not run catless personally, not just the environmental excuses but just because the sound is awful on these engines without cats.

 

no cats no problem

 

Just got off the phone with Magnaflow (45min conversation)
Turns out the 94106 Cat is made for OBD-I and NOT for our 05+ trucks that are OBD-II....
This wrong cat help accelerate the process of it going bad along with my miss in two Cylinders.

The hi-flow cat MAGNAFLOW Tech rep recommended is this one: 9906HM or the 99036HM for one with an o2 port.

if you need to spend the extra bucks on a better high material cat the 47106 cat is made for OBDII systems.