Tracus,
I am by no means experienced enough with Jags to with 100% surety guide you one way or another. It has been my experience that O2 sensors begin to fail around the 75k to 100k mileage. You have reported BAD gas mileage. This leads me to believe that the engine is running RICH and not burning all the gas being poured into the combustion chamber. If this has gone on long enough and a cheaper grade gasoline was used your Catalytic Converters could get saturated and no longer perform their intended function of burning up the toxic waste in the exhaust. (A catalytic converter provides an environment for a chemical reaction wherein toxic combustion by-products are converted to less-toxic substances. from Wikipedia) I had a vehicle with 120K and was running RICH and I replaced the Catalytic Convert and it returned to normal. Your ECM (Engine Control Module) depends heavily on the O2 sensors to determine the fuel/air ratios. What this means is that your ECM looks at the 4 O2 sensors and adjust the appropriate fuel/air ratio. In your case I bet you are running rich, too much gas. You have an O2 sensor on the exhaust header, before the cat, and one downstream, in the cat. The computer reads the first O2 sensor, before cat and then reads the second, in the cat. It then performs a comparison of the two sensors and with that data makes adjustments to the air/fuel mixture. This is a VERY simple explanation of how these devises play together. (Failure of these sensors, either through normal aging, the use of leaded fuels, or fuel contaminated with silicones or silicates, for example, can lead to damage of an automobile's catalytic converter and expensive repairs. From Wikipedia)(A dead sensor will prevent the onboard computer from making the necessary air/fuel corrections, causing the air/fuel mixture to run rich in the "open loop" mode of operation, resulting in much higher fuel consumption and emissions.http://www.autohausaz.com/html/emiss...n_sensors.html)

1) If you can smell gas either under the hood or in the tail pipe then you are running rich. Typically you would not be able to smell the gas.

2)If you have been running rich for ????? knows how long the CAT could be saturated and no longer effective, very little chemical reaction.

3)Catalytic converters from the Dealer list somewhere around $1100 each and you have 2 in the engine compartment.

3) If you replace the O2 sensors you should replace ALL 4. they run average of $110US each.

4)If you replace the O2 sensors the codes will most likely go away but if the CATs are saturated the codes will come back again later, once the O2 sensors have had enough time to get damaged.

CATs will normally not fail IF, the engine has been getting proper maintaince, and gasoline. This means regular oil changes, Good Gas 89 or higher octane (I prefer the 91 or 92), scheduled Tune-ups ie. replace plugs and do a thorough check on the engine for vacuum leaks etc., and don't forget that PVC valve. If you burn oil you can destroy your cats and O2s.

I hope this information helps you in your decision. If you have the extra money buy those cats on eBay if they will fit your year and have them put on by a muffler shop. REPLACE ALL 4 O2 sensors. Something to know, these "Front"/"Top"/"Upper" description refer to the same sensor, the one in the Exhaust header BEFORE the CAT and "Rear"\"Bottom"\"Lower" refer to the one in the Cat itself. These ARE DIFFERENT and you will need 2 of the "Front"s and 2 of the "Rear"s. I believe this is making reference to looking down the exhaust pipe from the engine.

 

jfenley,

thank you very much for your reply. It makes me understand how everything works.
Ok, the catalytic converter you gave me from ebay is for a 3.0 l. I called the company and they do not have it for 2.5 and I must look arround.
I also talked to one of our colegue in here and I am waiting for his reply.

I am really short in money right now ( I just spent over $5000 in this car already) so I will probably replace just that specifical sensor and the catalytic converter for the moment.

Yes I am running rich right now.

Regarding the vacuum leaks I don't think I have any because ALL the gaskets (inlet, camshaft, seal spark plugs) and o-rings on this engine were replaced a week ago by the dealership.
I have new spark plugs, new oil, new filter, new air filter, PVC hose, new valve and everything is brand new.

I can not thank you enough for your reply!

 

tracus,

I have similar issues with yours, i am getting P0420 (bank 1) and im really running low on my budget thats why I havent thought about buying new cat so Ive decided to buy the upstream sensor first then go from there.

Some people recommend the use of BG44k to clean your system although nothing has been documented for it to clean the CAT but when I used it, I could basically observe a considerable amount of added power when I drive. The P0420 code still comes back every now and then but I need to do one more step prior to buying new 02 sensors and that is by using SEA FOAM directly to the IMT. I got the idea from Thermo and I am currently googleing its exact procedure and the effectiveness of its use in cleaning the CAT so as to save me from buying a new one (or at least extend its life a bit further)

You have pretty much restored the optimum operating condition of your engine so thats one less worry about damaging a new cat in case you decide to replace it but I would look into changing the 02 sensors first and if you get to find the procedure in applying SEA FOAM in your IMT then do so and see if it helps remove the impurities in your CAT.

Just so you know, I am not a technician of any sort so I am just relying on my readings and feedbacks from this forum plus of course some random phone conversations I have with more experienced members so this post is merely an idea or a thought process and not a concrete solution to your problem (if you know what I mean.. )

Anyhow, take one issue at a time, dont let them scramble over you for you will just end up drowning yourself with frustrations... You just have to adjust your driving habits for now to fit the capabilities of your jag... it will eventually hit the road in its full blast..

 

Hello Guys,

As I promissed I came back with the results.
I do replaced the O2 sensor, erase all the codes from the computer. I use the vehicle for few minutes and the engine light is on again. I found a brand new catalytic Converter and replaced it last Friday.
Since then no codes anymore and the gas consumption droped from 16L/100km to 11.3-11.8 L/100km (in conformity with the On Board Computer). I assume this is kinda normal for this AWD vehicle.
I truly hope that the light will not come up again.

Bottom line, the code
P0430
CATALYST SYSTEM
EFFICIENCY BELLOW
THRESHOLD (BANK 2)
means you should replace the Catalytic Converter and with this one the O2 sensor too.



I thank you for all your suggestions and tips! They were very useful.

 

Tracus,
Good job!!
Thanks for letting us know the results. It really helps us all.