Dave_G

My 1998 LS 400 with 231,000 miles is showing a check engine light and mechanic is saying a cat is going out on one side. Forget the cost but it was high, so I was wondering if anyone has found some less expensive options to replace them than the dealer, and that will still pass emissions checks?

Thanks for your advice!

jaaa

What was the code that came up? I'm asking because I had a P0420(bank 1 cat inefficiency) code. It was a leak just past the cat where there is a flange connection going to the last cat. It is as simple as cleaning up the flange and putting a patch compound on to fix the leaks. I've found out that this is a common problem with our 20 year old cars. It's an easy fix that anyone could do.

Losiracer2

I added spark plug antifoulers to my post cat o2 sensors and that took care of the pesky CEL. Total cost was about 4 dollars.

You basically stack two antifoulers on top of one another and then drill out the second one to be able to screw in the o2 sensor. This basically makes the o2 think that its getting less exhaust flow, similar to a properly functioning catalytic converter.

dicer

And then there is the Rock auto option of after market catalytic converters, they don't break the bank with their prices.

Losiracer2

Having just replaced the EGR tube and experienced P0420 cat codes immediately afterwards, I would first try the antifouler trick.

Just removing a 20+year old catalytic converter is no easy feat. I first tried using my impact, which had no effect. Then used a butane hand held torch to try and heat up the nut, which did nothing. Then went to a full blown propane and then finally MAPP gas torch which was unable to free the upper nut on the passenger side. It is REALLY difficult to remove the cats.

Buying cheap aftermarket cats is easy, installing them is not.

dicer

To heat stuff you need an oxy acetylene cutting torch or rose bud nothing else will give enough heat, oh a carbon arc torch will but that's a bit of overkill.
And when directing towards the body in any fashion you will also need a thin steel plate to catch the heat from the flame else you could do damage to stuff.

sha4000

iTrader: (1)

I've been getting that P0420 consistently over the last 2 weeks but I'm pretty sure it's an exhaust leak right after the cat. I had an aftermarket Y pipe installed recently and I don't think the shop did a good job. I won't take it back to the same ppl so I'll eat the cost and find a better shop. The problem was that the aftermarket Y pipe did not have a smaller diameter pipe at the end that slides into the rear part of the exhaust. So now I'm thinking I have to find a shop that can either shrink the end of the after market pipe or weld a smaller pipe onto the end that can slide into the rear exhaust if any of that is even possible.

Banshee365

For the cat nuts on LS400's I've had the best luck honestly with just soaking the nuts and studs in penetrating oil for a few days. Removing the exhaust system is fairly easy in my opinion. Remove the 6 cat nuts and loosen the clamp under the back seat area of the car and remove the exhaust as a unit. I would do it that way then remove the cats from after it's on the ground. Cat's don't generally go bad without something else going on in the engine to prematurely tear them up. Has the car ever been ran for and extended period with a check engine light or anything?

dicer

I have a car that someone fixed a cat flange leak by welding it at least its only about an inch and half weld on the bottom area, yeah thanks guys. I don't enjoy fooling with some ones mess. Though I have made a few myself on projects I don't like just to get it up and running.

Scraape

read my build thread. i had P0420 & P0430 codes and cleaned my air mix path thoroughly and the CEL's went away. Must have not actually been the cats after all. Btw, i have a 1998 with 258,400 miles.
You can also try changing out the downstream o2 sensors as well if the first step doesn't work

Scraape

dont spend your money on a cat just yet!!