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[Brynjaminjones]

The XJ has just failed its MOT due to high emissions; apparently the cat is also rattling but I'd never noticed!

What is the advice on what cat to choose? I was told to go either for one designed for the Jeep, or for a high flow one. Is there any advantage to spending more on something like a magnaflow?

[bigjeepzj]

No save your money as you off road

[Dave69]

don't need to be jeep specific but as long as it fits, downside is that some cheap ones don't have all the required elements inside so not as effective. found that out.

[wildwood]

Take the easy route.....
Lighties......

Had to buy one for the YJ many moons ago.....l about £80 I seem to remember.

[Delk]

I have a high flow cat behind my storker and it passes the MOT every year. It does cost be a box of been are 20 pounds sitting in the passanger seat for the retest. Some day I will have issues but for now I am fine.

[JamesH]

I got a cheapo one from cats direct or similar that was fine for 2-3 years, about £60 delivered.

[Dave The Sparky]

I have a high flow cat behind my storker and it passes the MOT every year. It does cost be a box of been are 20 pounds sitting in the passanger seat for the retest. Some day I will have issues but for now I am fine.

Think the fumes coming from your cat have gone to your head

[Jonny Jeep]

ALL modern catalytic converters are high flow without exception.

The term was coined to differentiate between the early cats with a bead matrix, that were very restrictive, and the matrix type of cats (like the OEM cat) which are not. Using the term to market cats these days is just a ploy to part people with their money.

After having to replace two OEM cats after they cracked up and started rattling I opted for a Random Technology Super Stainless cat. Spendy, but being a stainless rather than ceramic matrix it won't crack up, and shouldn't need replacing again. It's a tiny thing in comparison to stock and it added a nice burble to the exhaust under deceleration which was a bonus.

[JamesH]

Ooh interesting, shiny parts I could buy

[Brynjaminjones]

I've ordered a £50 one on eBay, so hopefully that should do the trick.
I'm currently trying to get the old one off, which is fun.


I poked the O2 sensor, and it's wire came straight off at the sensor itself. As I've not managed to get it out yet, I can't see well enough to tell - will that be a case of slotting the plug back on, or will I need a new sensor too?

[wildwood]

Will be welded like a welded thing.........

Take it off with an angle grinder.......1mm slitting disc is your friend here

[JamesH]

New sensor would be my route, it will be a proper bastid to get out

[Bubba]

a big ginger tom should sort it

[Brynjaminjones]

Much time later and the cat is still stuck on there. I hate not having power tools!
My next approach will be to drill a series of holes to loosen it off.

As for the O2 sensor, I think it's definitely had it, and as James said it really doesn't want to come out! Looking at the "connection", I'm guessing it hasn't been working in a while, yet apparently the lambda results were good in the MOT
Would it pass the MOT without a sensor?

Also, where is best to get one cheaply, but ASAP?

[Brynjaminjones]

At last, the cat is off. Much usage of the universal tool (BFH), chisel, drill, screwdrivers, anger etc. and it's finally free.
I'd be very surprised if the O2 sensor was working looking at the way the wire was, and so I doubt it's been working for quite a while!

[jay140285]

Good work young man.

[Brynjaminjones]

Heh heh heh, starting the XJ with no cat or exhaust certainly gives holiday makers a shock! 
New cat has arrived now though, and O2 sensor ready for collection tomorrow.

[jay140285]

Now don't go following anyone through places at Cheapfest that will cause damage.


Sent from my iPhone using Tapatalk

[bigjeepzj]

No Jay thats your Job

[Brynjaminjones]

Haha, I won't follow you then Jay!


New cat is on, with old O2 sensor plugging the hole. I took it in to the MOT place out of curiosity, and it flew through the emissions test without the O2 sensor working!
Strangely, the check engine light also isn't triggered by not having the sensor 

[jay140285]

You getting ZJ to CF Dave?


Sent from my iPhone using Tapatalk

[Exdecuk]

Haha, I won't follow you then Jay!


New cat is on, with old O2 sensor plugging the hole. I took it in to the MOT place out of curiosity, and it flew through the emissions test without the O2 sensor working!
Strangely, the check engine light also isn't triggered by not having the sensor 

I run my 9er with a hollowed out cat and its never tripped the light on the dash either and thats OBD2 if yours is OBD1 then there is even less chance if all else is working correctly :-)

[JamesH]

It won't bring up a light or do much at all in my experience, I ran mine with no cat at breakout and all was fine (except the volume)

[Brynjaminjones]

Yeah, I've seen no symptoms of anything being wrong. I'm going to go ahead and replace it though, simply because I've put a deposit down on one, and it'll offer me peace of mind!

[JamesH]

I've still fitted a replacement cat, was just saying that the sensor isn't critical to engine, emissions etc.