This is the first time I've ever used/posted on a forum/blog site and I'm hoping that someone else out there has had some some success with the problem I'm facing.

I have 118,xxx miles on my '07 Dakota. 4.7 V8.
Recently got a PO430 code for catalyst efficiency below threshold. Rather than coughing up the $$ to replace the catalytic converter I ordered 4 new O2 sensors and replaced them myself. Ran some fuel injector cleaner in the gas tank. And installed new spark plugs. I erased the code with my coder reader and it hasn't come back.

However, I immediately got a PO300 engine code (random misfire) and the truck started running like crap. Idling in park is rough. When I put the transmission in Drive or Reverse, the idle is normal.
When I give it gas it starts to stutter and then drives okay once I get up to speed.
Compression on the cylinders is okay (120)
Ignition coils are getting a signal.
And confirmed there are no vacuum leaks.
With the engine running and in park position, When I uplug each ignition coil on the right (when facing the engine) the idle changes and then changes back when I plug it in. Leading me to believe they are doing their job. When I do the same to the 4 on the left side there is no change. Leading me to believe that the injectors on the left side are not supplying fuel. But when I'm driving it (giving it gas), they are.

I did clean out the throttle body with throttle body cleaner. I might have sprayed more than I should have wanting to make sure it was clean.
I'm not a mechanic, just feel like I'm somewhat mechanically inclined and can follow directions. But usually seem to know just enough to mess things up.

I'm at the end of my wits trying to figure out what to do aside from just replacing sensors.

Has anyone had anything like this happen to them or does anyone have any ideas of what I can do that won't tear a big a hole in my wallet?

Thanks.

Danny

 

Your catalytic converter is plugged up and not allowing the cylinders to properly evacuate. That's why you have random misfire and why at idle it runs OK, but when you rev the engine misfires because the cat won't allow enough exhaust through.

The only option is to replace or remove the Cat. You don't need the new downstream O2 sensors as they are operating correctly by signaling the p0430. The down stream sensors are only used to verify the converters proper function.


Does your truck burn any oil? Most converts foul out because of zinc and phosphorus contamination.

 

Initially, I'd focus on the areas I was working on. I'd look for anything that I had contact with, especially if it was harness related - sometimes things can get disconnected easily. Looking specifically at the areas you worked on, I can't see the oxygen sensors or cat giving you this type of symptom, so other than a connection check in and around that area, I'd put them to the bottom of my list. The throttle body however, has a couple of touchy sensors on it that can give you varying symptoms. I've run into problems with both the IAC and TPS on other vehicles that weren't easy to diagnose & static tests on the sensors were good. If you did anything with the IAC, it could be acting poorly in setting up an idle condition (if you pull these little motors apart, they're toast - the IAC is a stepper motor). The TPS is a very precise variable resister and when it starts to fail, it can give some really odd symptoms, but mostly, I had running issues rather than idling issues with a malfunctioning TPS.

I wouldn't hold any faith in left & right plug tests that you did - if one whole side wasn't getting fuel, it would run extremely poorly & by pulling off 1 coil on the working side, you'd only have 3 cylinders running - I believe it would stall in this condition, I've never seen an 8 run on 3 cylinders.

 

I forgot to mention that you can test if it is the converter by unbolting the pipe from the exhaust manifold and starting the truck. It will make a loud racket but if it runs good it is the cat.

 

Thanks Guys! I am still trying to figure this out.
When it's in idle, it runs rough. When I'm driving it smooth.

Yesterday, something under the truck began to start making a huge racket.
rattling and shaking upon ingition start up. When I got down to have a look is sounds like it's coming from the catalytic converter or something around it.
Possibly a chunk of the honeycomb maybe has broken free and is rattling around in the exhause maybe???

I haven't had a chance to mess with but I think I'm gonna have to go ahead and take it to the dealer and have the experts have a look. As much as I hate to do so because it seems like every time I deal with the dealership I leave there thinking I just got taken.

But at this point, I think I've done all that my limited experience can do and I hope they can fix it and have my truck running like it is supposed to.

PO430 came back last night. inefficient catalytic something or other bank 2.
The dealer said they can swap it out for 485 (aftermarket cat) and that's cheaper than I expected.

So we'll see.

Anyways, Thanks for the help.

 

Some converters have a heat shield that rusts off and rattles while sitting on top of the cat. Other causes of the rattle are internal to the cat where pieces have corroded and broken loose. Almost $500 seems like a lot for an after market cat - I'd suggest you get an alternate quote or two, I'd try a good muffler shop.

 

That was my thinking...

Good replies all around guys!

 

I have the same exact truck 2007 Dakota and 4.7 engine. Had a Complete Tune Up, Throttle Body Cleaning,,Still having Misfires. Runs great til it gets warmed up then Ill feel the misfire at full speed and on idle after a run. Going to get the Converter checked next.

 

To the OP, my magnaflow highflow cats were 80 a piece, add your average labor to install at an exhaust shop and I can assure you it will be much less than 485. The mags I got had bungs and everything, but I would recommend their spun cats for stock setup. No CELs to speak of as of yet.

 

+1 for Magnaflow converters. Cheaper, and work just as well as the expensive factory units. Had one on my 2001 Ram back in the day, worked perfectly without any codes.