Error Code 0430 - Cat Below Efficiency

[rmart]

I have a 1997 Ford Explorer V-6 SOHC with 100,000 miles that has run well with a few exceptions.

Recently, the check engine light came on and the code was confirmed to be Code 0430 (Cat Below efficiency). The Ford mechanic who is a friend inspected the vehicle while the light was on and performed a tune-up as the vehicle was due for the same. After confirming the code, he advised me that both cat converters needed to be replaced and he further recommended that I have a local custom exhaust shop replace the 2 cats as the same would be considerably cheaper than having Ford do it (again this was a close friend who works at Ford giving that advice).

After 3 weeks of driving with the 2 new cats the check engine light came on again...with the same code 0430. If the cats were both replaced what else would cause this code?

In general the vehicle runs well except it seems to have developed a stalling or rough idle problem at very low speeds (the last 2 years) when the vehicle has just started after sitting.

This rough idle is worst when barely idling and turning the wheels fully left or right (ie. like when pulling out of a parking space or our driveway). The vehicle will often struggle to run in such an instance and then die quite often when pulling out of a parking space/driveway from a cold start.

I have been advised this second problem might be caused by a throttle position sensor or Oxygen sensor problem. Is this an item that is a DIY fix item...if so what are the approximate costs and procedures.

What do you think are causing these two problems (and are the two related):

(1) the repeat error code 0430; and

(2) the rough idle and stalling (especially when the vehicle is started cold and wheels are fully turned).

Thanks in advance.

 

[ExplorerDMB]

The FORD name is defilently expensive. Anyway, the cat problem could be due to a malfunctioning O2 sensor. 100,000 miles is a good amount of miles on stock 02 sensors. You really need a scan tool that can retrieve all the data that is happening while its running. I would look at fuel trims, 02 signals and possibly MAF to get started.

-Drew

 

[Runnin'OnEmpty]

Yep, it could be the O2 sensor that's downstream from the cat. I would check the wiring harness that routes above the cat and goes to that sensor. Sometimes the wiring will sag onto or near the cat, and the heat will damage the wiring. Also spray some WD-40 into the wiring plug.

The rough idle/stalling is probably from a dirty IAC, which you can clean for a temporary fix. A search will turn up many threads on cleaning it. Also clean the inside of the throttle body, where the throttle plate meets the housing.

Welcome,
ROE

 

[Glacier991]

Understand what sets that code. The o2 sensor pre cat will vary in output voltage between roughly .2 and .7+ volts (ideal is .445, and the computer adjusts the fuel rate to attempt to hit that "perfection" so the voltage varies across that number as the computer chases it) However if the fuel is close to being right on, any unburned fuel will be consumed in the CAT (there won't be much if any) and the flow past that point, measured by the post CAT sensor will not vary, because there is no fuel left in the exhaust. The computer will run an occasional test to try and see if the CAT is doing it's job - looking for any variation in the post CAT 02 sensor voltages. If it sees them, it sets that code.

A fuel trim is the adjustment the computer makes to try and stay close to that .445v output. It makes long term adjustments (LT fuel trim) and it makes more frequent ones (Short Term or ST fuel trim). Fuel trims can alert you to a chronic lean or (as probable in your case) rich condition.

A good scanner can give you instantaneous readouts of these and other parameters. I think you are looking at some fuel system problem (though will admit an ignition problem could duplicate some of these symptoms)... a chronic over rich can kill a CAT... but yours may just be choking on too much unburned fuel and passing some, causing the downstream sensor to vary the voltage.

I'd be curious to know your fuel rail pressures.

 

[rmart]

rmart

Thanks to all for your prompt and detailed responses thus far. I remain at a loss for what is causing my 2 problems. I posted the same question on a DIY forum and the consensus for my CAT problems was simply that I have an aftermarket CAT and I should have installed a Ford Cat which would have been OBD II compliant. All on that site said, go back to the custom exhaust shop and have the cats pulled for Ford cats instead.

As to my idle and stalling problem, I was told that I need to replace the upper and lower intake manifold gaskets and further that an o2 sensor will not fix my problems and would be a waste of time or money.

What was meant by "fuel trims" as posted by ExplorerDMB?

 

[rmart]

rmart

anyone else have thoughts on what is causing the 430 code or my rough idle? Your input is greatly appreciated to this newbie.

 

[Glacier991]

I thought I explained fuel trims. If not, I added some older threads on computers and the like to the new sub forums on computer engine control, I suggest you read those.

The advice you got was good insofar as the don't replace the 02 sensor just yet..

While intake gaskets might affect the pre-cat 02 voltages, it would likely be a lean condition, and should not affect the post cat 02 voltages. If it isn't the CAT's, I am thinking you have to be over-rich somehow.... like a fuel pressure regulator problem or something... but... hard to tell. In the end it may be the CAT's, I dunno. At this point you got my best thinking.

 

[ExplorerDMB]

Just a small note on fuel trims - usually most of the time you read the long term fuel trim when diagnosing. Short term is too quick and isn't really useful.

-Drew

 

[Glacier991]

Good point Drew.... short terms are more of a curiosity... long terms tell the tale

 

[Billy177]

just keep in mind that some aftermarket cats are just simply not as efficent and can also set off the check engine light

 

[edd189]

So is replacing the O2 sensor the correct way to clear this code? I never heard a resolution.

Edd

 

[edd189]

So is replacing the O2 sensor the correct way to clear this code? I never heard a resolution.

Edd

 

[edd189]

So is replacing the O2 sensor the correct way to clear this code? I never heard a resolution.

Edd

 

[Col]

edd189.

I think you have to check your O2 sensors.. pre-cat and post-cat, check connections, clean them, also, check if your IAC Valvle and Air Intake Body and MAF Sensor are clean.. after that.. you can scan codes, clear them and wait if the 0430 comes again.

Jorge
AKA: Col