Britdog15

okay im getting pretty mad ive replaced the plugs wires and the coil pack, ive ran fuel injector cleaner and checked the injectors with an ohm test and they were at the same. they just keep coming back. the code came on the first time and i replaced the plugs and wires because it started to have a small back fire. it cleared the po308 code for about 2 or 3 months and the po430 kept coming back every so on. Now i have no idea what to do. should i replace the cats or even cut them off? im just dumb founded right now. thanks guys

piledriver

Your car is almost 12 years old. How long have you had it? Forever? Or did the previous owner take care of it, or beat it, like most poor SOB's do to they're Mustangs? At that age the car is reaching it's time to rebuild or junk it and get something newer. Your car is only worth a couple $1000, unless you put a lot of mods into it. You seemed to have fixed the #8 cylinder misfire; If you really love your Mustang(who doesn't), I would replace the cats, as cheaply as possible, but still do it correctly. What mods do you have?

devongarver

This is 100% a damaged or clogged CAT. Try banging on the CAT with the palm of your hand and listen for a rattle, if you hear a rattle, the honeycomb is cracked and crumbling-needs replaced. Also check for cracks along the bottom, running excessive fuel through there can damage the whole housing as well.

There are a few solutions here.

1. Take to muffler shop, have both cats cut out and replaced with 60$ aftermarket universal cats, problem solved for about 250$ parts and labor.

2. Purchase aftermarket catted x-pipe for around 350-400$ and install yourself.

3. Purchase Off-Road(catless) X-pipe, for about 200$ and install yourself, but you will not pass emissions this way(if you have emissions testing where you live). Even if you purchase the MIL Eliminators to make the light go away, the O/R x-pipe still can't always fool inspections if they use the mirror under the car.

It just depends what kind of budget you are on. If it were me, I would get a nice catted x-pipe and call it a day.

Britdog15

rebuilt motor with about 7k on it
bbk cold air intake
bbk throttle body
trick flow plenum
bbk underdrive pullies
straight piped
autometer gauges and tach
just put new wires plugs and coil packs
the car runs like new its just these codes keep popping up and i want to fix it

piledriver

Good.... you rebuilt the motor, that's a really good thing. I just hope you forged the internals; in my humble opinion, if you used those crappy rods and hypereutectic pistons, and believe me, I hate to say this, but I think you wasted your money. For a few $$$$ more, you could build the sh*t outta that motor and not worry about busting something. Good luck fixing the cats, buddy.

Britdog15

Okay i was thinking about getting mil eliminators from AM and then taking my cats off and try to get everything inside them out and clean it up and then put the cats back on. Just something i thought might help my problem. also i might try seafoam since it says it will clean out carbon build up

Boneyard1972

I know this is a old post but wanted to add my PO430 prob. I purchased a used 07 Mustang with 4.0 . I had it a couple weeks and noticed at a steady speed on the interstate It would jerk every now and then. Code started to pop up saying misfire. I replaced Plugs, Coil , Wires etc. Still no change. I dealt with this prob. for 6 months or so and one day I was heading home from work car started running with more power than it ever had and them quit. It jumped time! Well I found a 4.0 in a wreaked 08 Mustang with 58,000 miles on it. I bought the motor put it in the car started it up ran great. After driving it a day or two I noticed that the throttle response just wasnt like it should be. Then here we go a check engine light. Pulled the code and it was a PO430 Catalysis Operating below Threshold Bank 2. Well I started doing my research and using a Heat gun checked before the Cat's and after reading the temps. I found that the Bank 1 cat was hot like it should be but the Bank 2 cat was not heating up at all like the Bank 1. I found this odd. So after much hesitation I purchased the Walker EPA Ultra Direct Fit Convertors Part # 50554 from Carquest with is the same as Advanced Auto now. It was the complete assembly. From the exhaust manifolds , both cat's and pipe to where it comes it the single pipe. Perfect fit used all factory hangers and the factory clamp where the straight pipe connects. I have a friend that owns the Carquest and he sold it to me for $350.00 regularly Around $450.00 . I pulled old cat's and pipe out and replaced it. Started car up and cleared code. Taking a flash light and looked in the pipes to the Cat and noticed the Drivers side where I was getting the PO430 for had nothing left inside the cat. It was gone burnt out. The other cat looked great. Light never came back on after driving a couple hundred miles no light. But I noticed the throttle response was still not there but no trouble codes. I got to think if all this burnt out of the cat where did it go?? In the muffler thats where!!!! So i went and bout a Flowmaster 40 and pulled old muffler off and installed new muffler. I took my light and looked in the inlet of the old muffler and sure enough it was full of parts of the Screen and all that junk from the Cat. After this wow what a change in throttle response and HP etc.
I just thought I would share this with everyone. If you have a PO430 OR PO420 get a scanner and watch the up stream and downstream O2 Sensors and it will tell you what you need to know. Upstream Should be steadily fluctuating while the downstream should be holding more of a straight line voltage. if your upstream o2 and downstream and acting the same on your scanner then its your cat plugging up or just not doing what its suppose to do anymore and that is where your code is coming from. I would have saved myself a lot of work if I would of had a scan tool and did this. Anyway hope this helps someone..
Thanks...