Hi everyone, been battling with the P0430 Catalyst Efficiency Below Threshold for nearly a year now and starting to run out of ideas. So here I turn to you guys for some help

I have gone through most posts I could find on the subject to figure this out but without much luck. Some further detail below on what is happening and what has been done so far.

Originally started with a P0420 code. I have then replaced both O2 sensors (up and downstream) with the exact matching Denso ones, for that relevant catalytic converter. Problem gone. Few weeks/month later, P0430 code started.

To fix the P0430 code, I have also replaced both O2 sensors (up and downstream) for that second catalytic converter with the same exact matching Denso ones. Fix did not work. Tried some specific catalytic cleaner fuel additives (CataClean and BG44K a couple of times) and also did not work. Made a simple home-made smoke machine (using the soldering iron in a jar with baby oil method) to try and spot any vaccum leak around the engine. Granted it is not the most professional smoke machine, but nonetheless no apparent leak could be spotted.

As for the symptoms, outside of the P0430 code (no other code just that one by the way), exhaust fumes are quite sooty. Tailpipes and boot lid tend to becomes black covered with soot overtime. If I floor the acceleration pedal I occasionally get a light greyish/black cloud at the back (but not all the time) and if I do this while the windows are open, I can also smell petrol (also not everytime). Forgot to mention, it had also failed its MOT on emissions. If I recall correctly CO levels were too high at high revs (motorway speed equivalent).

Car seems to be running fine other than that. I don't feel any loss of power. Idle had been rough on start ups but seems to have been fixed since replacing the defective PCV valve. Idle seems to be fine no obvious signs there.

The more I look into it, the more it seems that the actual catalytic converters are at fault. But given the price of these, I'd rather be sure I haven't missed anything else before jumping to that conclusion. I've also been told by mechanics (on various trips to the garage for other reasons) that the engine is running too lean but they haven't done a proper full on diagnostic for that matter.

Cheers for your help

 

yep…. how many miles on your car? Perhaps its not the sensor… but the cats.
Doubly so, if you’re running too rich. Or if you have a faulty injector.

 

Car is on 87k miles now. how could you tell if it is a faulty injector?
Forgot to add, all eight spark plugs have also been changed for the correct NGK iridium ones. That's another thing that can be eliminated.

 

Catalytic convertors don't last for ever, on my 96 X100 they managed 15yrs until 2011 and 90k miles

Roughly the same time as your 2007 X150

Just a shame they are so expensive and a requirement for our MOT t have fitted

 

And I’m on my 3rd set in 150000 kms. of course I’m known to not be kind to them.

 

You COULD try a few cans of Catalytic Converter Cleaner. Supposedly it works well about 60% of the time.
https://smile.amazon.com/Dura-Lube-H...NrPXRydWU&th=1

 

Have the same issue I have a spacer that one day I will install and see if that helps.

 

Measure fuel trims (for hints). They may be out by enough to cause issues but not enough to flag other codes.

Do the usual: hot engine, parked, at idle and then again at about 2500rpm.
LTFTs (& maybe STFTs) can be very revealing.

But first make sure it is running CL (closed loop)! If not it has to run rich and that'll eat cats.

 

Plugged in my generic obd reader last night, checked a few parameters but didn't think about the fuel trims. Will have a look at that this weekend.

Out of curiosity, if the final verdict is indeed replacing the cats, anyone tried fitting some magnaflow weld on high flow cats? I have heard it had been done with success, but little information to go by. I would be tempted to try these magnaflow cats, but the list of cats available on their website is huge! And have no clue which model would be best suited.

 

Can your local set your fuel trims or does it have to be a dealership?

 

A hard reset does reset long term and short term fuel trims.

 

They will guarantee it doesn't run right.

 

The dealer can clear them or you can (battery off). Not a very good idea as you also clear the smog info and force the car to relearn. So then you get to wait until it has done the relearn to see what they now are when you could have left them alone and just read them.

 

Most basic OBD2's will show fuel trims on both banks. If your LTFT's are off more than -5-10% you likely have a vacuum leak; + 5-10% could be a slow acting injector (staying on too long). They don't code until 20% off. Correctly operating LTFT's should always vary near 0%, or +- 1-2%, where you achieve stoichiometry, a weight of air to weight of fuel of 14.7:1. Note this is a naturally aspirated car; I don't know the data on a supercharged one.

Smoke machines need healthy pressure to work well. A cheap $100 machine from Amazon is a good place to start BUT its likely to miss issues until you pump it up solidly. The rubber glove over the throttle body does let enough pressure build. Use a 3" plumbing cap from Home Depot on the TB. Not sure if it will reveal a problem, but I am sure that low pressure (like a bicycle pump) is not enough to be a reliable indicator. I had a bad injector oring that didn't show until the vacuum envelope was very solidly pressurized.

 

valves could be gummed up on intake I cleaned them and my cat code went away

 

Thanks for the suggestion Ian did you clean them yourself or have a shop do it?

 

I did it myself while I was there I also changed the hoses and all the plastic bits

 

Ian, how did you clean the intake valves?

 

All interesting suggestions. I have been playing around with the OBD reader. All seems fine. LTFT are slightly different between each bank, but readings are all around 0% (occasionally goes up to 1.7%), the engine does run in close loop and the fuel/air ratio is is between 16.4 and 16.8. At idle my vacuum holds at 34kPa which seems fine to me then drops as I press on the throttle pedal. Nothing seems to be out of place, except for that bank 1 post catalytic O2 sensor that oscillates a lot compared to bank 2 that is much more stable.

I have taken the car to a shop yesterday, that I can trust. And from my explanations and them reading the codes they concluded it is the cat. I might just bite the bullet and get the cat replaced see how it goes. Going to get some weld-on hi-flow sports cat fitted, waiting for the quote to come. Cheaper than the Jag cats, and if it does not fix the issue, at least I know I'll have brand new cats (can tick that off the list) that will release some extra power and more noise hehe.

Ian, do you have the 5.0l engine? I might be wrong on this, but I thought intake valves on the 4.2l (the one I have) would be sort of self cleaning due to the fuel injectors being placed before the intake valve, and therefore the injected fuel helps keeping the valve clean. As opposed to the 5.0l engine which is direct injection and as such intake valves can get dirty since the fuel is directly injected in the combustion chamber and not before the intake valve. If I'm wrong I'll add the intake valve to be check on my to do list.

 

So I guess that's a big NO on trying one of the hundreds of 60% reliable Cat Cleaner liquids.
$15 vs $2000 X 2 seems like a valid reason to at least TRY though.
Oh well.