Hi,
My 1985 Slll XJ6 4.2 (Canada) has a Cat fitted to the exhaust manifolds and it houses the Oxygen Sensor. The unit has a leak and is in pretty bad condition. As the car is over 30 years old, it is no longer necessary to have it emission tested.
Can I just replace the cat with a UK style pipe and weld on an O2 boss to accept the sensor? If so, is it a straight swap and where can I locate on (budget in mind)?

 

I did just that! Not sure if i wanted to or had to, swap out the y pipe too, the one that goes from the downpipe to the front mufflers.
Got all my stuff from Pauls... years ago though!

 

I had the converter opened and cleaned of the stuff inside, then rewelded and pressure tested for leaks, reinstalled it and the 02 sensor, done.

they always start to separate at the bottom cap where it meets with the Y pipe, and that's where you open them to remove the junk inside. Careful though, the stuff is toxic like hell. (my mechanic's advice).
I used double gloves and a respirator filter to remove the bag inside which is rivetted to the inside. After all that, the car runs a lot smoother and it "looks" like the converter is still in use. I did replace the Y pipe with a European Y pipe, catless, another improvement. Also had the new Y pipe and the over-the-axle pipes coated inside and out by Jet Hot Coatings with their Sterling ceramic coating, it eliminated the hot spot under the driver's floor. Exhaust is very smooth now. Probably gained a couple horsepower.

 

The drill and weld technique works,


1. Yes, a UK pipe sans sensor should accept a bung for the sensor. but, availability this side of the Atlantic?


2. A competent muffles shop can bend up the piped, drill it and weld in a bung for the sensor.


3. When I did my conversion, I got two down pipes, one fore each bank of the V8. Sourced from Sun Coast in Punta Gorda, FLA. Clearly, made by a vendor to them. Beautiful workmanship. But, alas no bungs for the needed O2s. I figured out a location and drilled a hoe to match the nose of the sensor. MY conversion kit came with bungs.
I used my oxy acetylene torch to weld them in place. When I put the pipes on, I realized I could have located them better, but it works, so, all is well there.


4. Although Jose pulled of his "gut the cat" project just fine, that would be my last option. As stated, bad stuff in there....


Carl

 

the Euro down pipe, the one from the manifolds to the Y pipe is also available, but European cars don't use O2 sensors, as far as I know, so they don't have the threaded hole for the 02 Sensor, that's why I decided to reuse the catalityc converter as a down pipe.

 

You are correct, i just welded the bung on

 

1. I forgot, if I ever knew, just what does the sensor do? An emission thing to trim the ECU? If that function no longer needed, just omit it.


2. As Jose's "gut the cat" works', great. But, as Jose has cutting and welding tools and skills, just use a hole saw and cut the bung from the old pipe. cut a similar hole in the new pipe and weld in the old bung.


Carl
Benefit, fresh steel to prolong the life of the exhaust.

 

Right, the oxygen sensor is for constant trimming of the fuel mixture.

If the ECU does not see a signal from the oxygen sensor nothing horrible will happen but the system defaults to a pre-written 'fueling map'.....which generally is a bit richer than ideal. The engine will like the richness in some situations....but not so much in others. I wouldn't suggest omitting it, personally, unless a non-emission ECU is installed....which probably wouldn't be too hard to source from overseas.

Cheers
DD

 

Thanks for the clarification.


When I took my failed DOHC out, I removed the O2 sensor. It was loose in the bung. Probably non functioning for lack of a good ground. And, indeed, the at ran just fine, til it failed for an unrelated reason. Howe it got by the dealer's required pre sale SMOG is a mystery. I have a clue, though !!!


Carl