Dear All,
I've recently purchased a 2003 X-Type 2.5L Sport; my first Jaguar. I bought the car for a reasonable price (2000.00 USD) because the Check Engine light was lit. The code was "P0420: catalyst system low efficiency", or something of that nature. I have been bracing for the financial impact of a cat. system replacement.
I have used premium fuel (93 octane) since I've owned the car, have used a fuel system cleaning agent, and have recently realized that the gas cap needs to be tightened until 3 clicks are heard.
PRESTO! No more engine light!
Have I dodged a very expensive repair bullet? Has anyone else out there had a similar experience with this code?

 

What kind of mileage on the car? were you able to get any maintenance records from the PO?

 

Neither the octane rating of the gas nor a loose fuel cap should create/eliminate a P0420 code.

 

MikeinPA, please keep in mind that the X-Type computer needs 5 "run cycles" (ie, start the vehicle, have the engine run, car driven for about 5-10 minutes, then be turned off) without the error appearing in that time. On the 6th start, if the error code has not been seen as mentioned, the light will clear on its own. The fact of running a cleaner and 93 octane fuel (assuming the person before you never used a cleaner and was cheaping out on gas) may have been enough to make the engine happy again.

Some may recommend to be safe to use a can of Seafoam through the intake to make sure that the cats are cleaned out. But, that is up to you.

As for the link between the gas cap and the codes, like was mentioned, the two are not related.

 

Sorry to disagree.

The health of a catalytic converter does not depend on type or quantity of gasoline additives. The amount of additives has nothing to do with octane ratings. Both concepts are old myths.

Seafoam (a mix of light oil/naptha/rubbing alcohol) will not have any positive effect on a modern engine. The unburnt oil, which is what produces the clouds of tailpipe smoke, may in fact make a marginal converter worse through contamination.

 

Geewillicurs,
The car has 129,000 miles at present, but the engine was replaced roughly 30,000 miles ago. I do have the maintenance records for the car, but I have not read through all of them to understand the history of the car.

 

Mikey,
Could the Seafoam have any cleaning effect on the oxygen sensors of the car? I can't think of anything else I have done to the car that could make a difference in cancelling the light.
Thank you.

 

Thermo,
The car has run well since I bought it: lots of power, no stalling or faltering, smooth idle.
I don't know how to explain the change, but I think it proves my irrational belief that vehicles are living things, and will operate properly when given kind words and loving gestures from their owners. It doesn't make sense, but there it is!
Thanks for the support and information.

 

Mike, you probably have/had an intermittent issue and you the met the drive cycle conditions for the light to go off without the condition present. I wouldn't be surprised if it came back at some point soon, but you never know.

Here is the drive cycle conditions for the O2 sensors:

HEATED OXYGEN SENSORS MONITOR DRIVE CYCLE
Upstream (Universal) oxygen sensors:
1 Engine OFF; cooling fans inoperative > 20 seconds.
2 Start engine and bring to normal operating temperature > 82 °C (180 °F).
3 Drive the vehicle between 3000 – 4000 rpm at a steady speed. Lift foot completely off accelerator and coast to a stop within 30 seconds. Do not touch accelerator
pedal for 4 seconds after coming to a stop.
4 Repeat step 3.
5 Idle engine for 11 minutes.
Downstream oxygen sensors:
1 Start engine and bring to normal operating temperature > 82 °C (180 °F).
2 Drive the vehicle steadily between 48 – 97 km/h (30 – 60 mph) for 10 minutes.
3 Drive the vehicle above 3000 rpm in 4th gear at a steady speed. Lift foot completely off accelerator and coast for 30 seconds.
Oxygen sensor heaters:
1 Start engine and bring to normal operating temperature > 82 °C (180 °F).
2 Idle engine for 3 minutes.

 

Not a positive effect. Possibly negative.

If you've got a bottle of Seafoam hanging around, the 1950s just called. They want their additive back.

 

On all my modern cars, seafoam through the intake makes night and day difference.
Best $6 one can spend!.
And yes, i use premium fuel and a synthetic oil change every 3000

 

Never underestimate the placebo effect.

 

Dear mikey,
Do you have a fuel additive/cleaner that you recommend? Or do you recommend using no additives?
Thank you.

 

NO additives of any type. Ever. Just like it says in the owner's manual.

Two points:

-Modern engines run extremely cleanly in their own right as a product of design, materials, machining techniques and engine control technology which was not available 'back in the day'. That's why they get such good mileage with such low pollution levels and without consuming oil between changes. Engine failures or overhauls are pretty much a thing of the distant past

- Modern fuels and oils are light years ahead of what was available (again) 'back in the day'. Today's clean fuels produce almost no deposits in the first place, but the additives that all brand name fuels contain are more than enough to keep an engine sparkling clean.

All of this means that there's nothing left behind for any bottle of snake oil to affect one way or the other. Can't fix what's not broken, in other words. Most (not all) of the bottles of additives seen on store shelves are simply concentrated versions of the same additives already in your fuel. A full tank of fuel contains around twice as much additive as a typical bottle off the shelf- at an outrageous price of course.

There's one notable exception to the above- the all-hailed Seafoam.

It contains NO additives of any type that would be capable of removing deposits or contamination even if they did exist. As posted above, it's 50% light oil (not a good idea if there's delicate sensors in the area), ~25% naptha and ~25% ordinary rubbing alcohol. That's it. No miracles.

If you look up the history of the company,

https://seafoamsales.com/about-us/

you'll see it was developed to clean the carbs on WWII vintage 2 stroke outboard motors which gummed up in storage. It does work very well for this purpose if you let the carb soak in Seafoam while not being used. It still works well for chainsaws, weed wackers and other two stoke devices that are essentially unchanged from the dark days of technology.

Why do people ('Foamers) use it in modern cars and insist that it performs miracles?

I'll be farqued if I know.

The myths and misconceptions about fuel and oil are legendary. Some people still think that gas was better back when it had lead in it. Some are convinced that high octane fuel has magic powers.

There's others that refuse to use E10 (10% ethanol alcohol) fuel, yet think it's a great idea to dump Seafoam (containing alcohol) in the tank.

Maybe it's because Grandpa swore by it for his Massey Harris tractor?

Maybe it's the grand smoke show coming out the tailpipe which is simply the oil burning off? Wait a minute- if an engine, converter or sensors are already contaminated- why would a sane person put oil on them which might make the contamination worse?

Again, the placebo effect has been well documented and usually comes with a few 'butt dyno' comments. I expect to see these next.

If an additive costs $10, the car has to go $10 faster, right? Same thing as shiny $200 add-on under hood devices. They always make the car feel faster- otherwise it means the owner got ripped off. Oldest marketing trick in the book.

Save your money.

 

Dear Mikey,
You are wise in the ways of the fours (and sixes, and eights).
Thank you for the information, I appreciate it. I will read the owner's manual, which I have not done so far, and follow the recommendation of no fuel additives . Those who made it should know it best.
Thanks again.

 

Again, More flawed self hyped opinion...

These cars were also supposedly design to run for life on the same transmission fluids, Transfer case Lubes and differential Lubes Never having to changes the fluids and lubes...Well I invite you to read the hundreds and hundred of posts and topics here regarding these issues on failed transmissions and transfer cases for lack of periodic servicing and fluid changes...To say the Owner's Handbook is the final say so on what is right and wrong is Ludacris and will lead you to ultimate failure..

Use a good Fuel System cleaner such as BG 44K and feel the difference for yourself...Or better yet..Talk to a Jaguar dealership's service guys and find out that they USE regularly, the BG44K fuel cleaning system in ALL the Jags that come with fuel related problems or for simple preventative procedures.

 

Ah- the peanut gallery chimes in again. As usual, your attempts to make a point comes down to comparing apples to oranges are as such are misguided.

There's plenty of historical evidence demonstrating what happens when fluids are not changed at certain intervals.

There's no evidence supporting the appearance of problems where no supplemental fuel or oil additives were used. Similar to your previous claims of 'doom and gloom', I'll ask you to indicate where are all the badly running cars are hiding, given that 99% of owners do not use additives of any kind. How come persistent check engines lights always prove to be a mechanical or electrical fault and not something that can be cured with a $10. miracle in a can

My Jag dealer had a vast array of products on the shelf and always tried to upsell me on at least 3 or 4. Funny that they could never answer why they promoted stuff that contradicted what Jag advised- and how come my car ran just fine without them. I asked them to put in writing that use of such products would not void my warranty. They refused.

How comes Jag endorses Castrol lubricants but not BGK products?

I await your next conspiracy theory.

 

Having tried a number of additives, have yet to find one which does not make the car run like it has three cylinders for a few miles, after which, normal service resumes and no noticeable improvement.

 

Aah..the ***** gallery is back with his infamous; "I have to have the last word.."

Wake up buck-o..the topic was fuel and not lubricants. Didn't your schools teach you to read? or was it you teaching them? .....The example about Filled For Life Lubricants was just ONE example of how things are held as gospel in the Owner's Handbook and some of us came out of winter hibernation have realized this......But the Engine oil is the only Lubricant mentioned to be Castrol..But the topic wasn't even about that, now was it buck-o? Take your spin doctor crap somewhere else will Ya


Stand by folks, Dudley-DO-Right will pipe in with the last word, again!!

 

Seafoam is super awesome.
You should try it.
Rather than listen to negative nellies, your own experience will tell you the answer