Fairly new here (I reference a lot of posts though) and new to wrenching on exhaust systems so I am reaching out for clarification or tips.



2007 Jeep Wrangler 3.8L (~200,000km's)

P0430 code



O2 sensor info off OBD live data:

B1S1 good

B1S2 good

B2S1 good

B2S2 NOT good = fluctuates from 0.2 to 0.8 intermittently. @ 2500RPM it becomes worse and fluctuates all over the place rapidly.



Fuel trim off OBD live data:

STFT1 good

STFT2 good

LTFT1 NOT good = 13.3

LTFT2 NOT good = 7.8

--> Go to 0 immediately @ 2500RPM<--

(STFT both go up @ 2500RPM but that has to be normal operation?)



So with this in mind, I am running in a LEAN situation



Potential problems:

-MAF sensor

-O2 sensor faults

-vacuum leaks from intake

-dirty injectors

-fuel delivery issues

-cat



I am wondering if anyone can help me streamline the guess work knowing this information. I'm assuming others have walked this path.

I really don't have experience with exhaust etc



Thanks

I can’t help much here, but I’m having the same issue. I’m going to a muffler shop today to have them check for exhaust leaks. I’m having a slight stumble so am also going to maybe replace all my plug leads - I believe that misfire/poor spark can cause a P0430.

Ian


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Your P0430 code is for your Catalytic Converter Efficiency. Don't get too wrapped up in the Fuel trim numbers.
Look at the live data at the B2S2 data. Capture that and graph it. Then compare that graph with the B2S1 graph data.
Make sure the Jeep is warmed up and in closed loop operation. Now drive a short distance on the expressway and watch the data.
In most running conditions, the S1 data will fluctuate up and down significantly, while the S2 data should remain constant at around 600mV to 700mV. If the S2 graph is mirroring close to the S1 data, then your cat converter is no longer doing it's job and needs to be replaced.
If the S2 graph fluctuates with little to no resemblance to the S1 graph, then you have a leak post cat, pre sensor, or the sensor itself is bad.
Vacuum leaks and fuel issues will set off a lean or rich bank code well before it kills the cat and sets off the S2 sensor code.

 

I have a bit of a challenge with this. My Jeep is a Federal vehicle (meaning it’s not a CA vehicle). The PO had installed after-market headers, cats, and cat back exhaust. There are no manufacturers of cats that offer an after-market option that is CARB certified. So...if it is a cat going out, and that does seem likely, and the cats are dealer only parts, then I may have no choice but to go back to full stock, maybe even including new manifolds, and have it all installed at a dealer. That will get very expensive.

I have checked the live data using my ODBII monitor, it doesn’t have charts, and I don’t have any way to export logged data (I am Mac only at home). B2S2 does seem to fluctuate a little more than B1S2, although it’s really hard to tell. I’ve tried two new O2 sensors in that spot (long story) with no discernible difference in behavior. It does seem that the issue is deteriorating because I ran code free for a month, but now it comes back in within a few cycles of a reset.

My local muffler shop doesn’t seem to want to check for a leak, maybe I’ll lean on him a bit more.

I think my next step is probably to change the plug wires to see if that gets rid of the stumble and try a code reset. Probably check the plugs while I’m at it.

I might also try switching the upstream sensor, I have heard that an older (less sensitive) sensor upstream and a newer (more sensitive) sensor downstream can cause issues.

One other datapoint, when I first start the Jeep and reverse out of the driveway I do get a pretty strong blast of fumes with a bit of an unburnt gas smell. This may be normal with the roof off, but I don’t remember that from last year.

Ian


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Subscribed!

 

If I take my Jeep for a spin while monitoring sensor reactions (as was suggested above), the cat may be diagnosed as faulty.

In an effort to avoid "this" situation again, I am wondering what steps I can take to deal with whatever degraded my cat upstream. Was hoping that my trim info would narrow down some options. I realize there may be a number of things causing issues but hoping someone with experience can zero-in on some likely causes.

 

To the OP, i wouldn't worry too much about avoiding this type of maintenance in the future. The cat lasted over 125K miles (200K km) so its led a long life.

As for your trim numbers, I don't really worry about LTFT numbers unless they are above 10-12 and below -10 -12. Its is interesting that your Bank 1 numbers are a little high (lean) but Bank 2 is in the normal range, yet Band 2 cat went out. Over rich cylinders kill cats faster than lean. The unburned fuel ignited by the cat element usually kills cats.
Are you looking at the STFT and the LTFT at steady and constant speed after closed loop?
I find it best to watch them on a graph and look at overall average, rather than instant points, as speed, RPM, load, IAT, ECT, ambient temp and other factors fluctuate the Fuel trim numbers greatly. I usually test drive the cars on an expressway at speed with the cruise control on, to capture that sort of data.

After you replace the cat, clear the computer and watch the numbers. If your fuel trim numbers continue to run a little lean, look into a possible vac leak in the intake ducting, intake manifold or throttle body gasket. Run propane around the areas while watching the O2 sensor data.

Maddog2020, start a new thread and we can try to help you.

 

Thank you for your time here.
My LTFT was above 12 and the other figure was ~8

Still proceed with the cat before other options?
(I'm 99% to the shop for a new cat....just tight on cash so wanted to confirm that number once more)

 

Yes, do the cat, then move on to what comes after that.
At least your "Cat Efficiency" code will be cleared.
After that, if you get a lean bank 1 code, we can tackle that, knowing that the cat issue is not causing that problem.

 

Well, having changed my plugs and wires I took the Jeep through the drive cycle tonight and all the monitors passed cleanly, including the catalyst. No P0430. Makes me wonder if the bad plugs/wires were letting unburnt fuel through and it was too much for the cat to handle so the downstream sensor was getting too much variation. Anyway, I’m hoping that was it, and my cat isn’t bad....

Ian


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Follow up:

After looking at the OBD figures for a while and thinking about fuel trims, I decided to replace the o2 sensor downstream instead of jumping on the cat right away and I have been code free for a week or so.

 

Quick update. 2 week’s since I changed the plugs and wires and no P0430. Go figure. I guess it’s super hard for the PCM to calculate anything to do with emissions when the motor isn’t running right.

Of course as soon as this one disappears my other car (BMW 335d) throws a glow plug code and those things are a total nightmare, you have to take the intake manifold out to get into the middle of the motor and then remove the glow plugs while the heads are at normal operating temp. How the heck I’m supposed to manage that is beyond me.


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Quick update. 2 week’s since I changed the plugs and wires and no P0430. Go figure. I guess it’s super hard for the PCM to calculate anything to do with emissions when the motor isn’t running right.

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Well balls. Looks like I spoke too soon on this. P0430 came back this am. I bought a Bluetooth OBD adapter and will datalog and graph the O2 sensor voltages when I get it. I’m not going to throw parts at it. I do think it’s quite likely that I do have a bad cat unfortunately. The PO replaced the motor because of an issue with oil flow on Bank 2, so it seems plausible that the cat got fouled with oil and is dying. Oh well. I’ll know more when I get the charts.




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Redneck leak check: empty shop vac in reverse (blowing) duct tape hose to muffler tip. Spray bottle with soapy water and spray everything and look for inflating bubbles or if bad enough it just spits at you. Do this whils the exhaust is cold.

 

I had the exact same problem with P0430. I analyzed everything exactly, examined the catalytic converter with a camera, leak test everything ok. By chance I discovered the error, namely a spark plug was not fully tightened and the engine sucked in oxygen when the engine was braking.

i have always seen the effect of datalogging with Bosch Esitronic with the lambda probe B2S2 but could not find the cause. At P0430, look at the spark plugs or their strength first, it is the cheapest and easiest.