catalytic convertors

[nutbar78]

So these R51 V6 trucks have 4 cats right? If one or two go bad, can't we just put some plain piping in with a threaded bung for the O2 sensor? I mean instead of replacing the cats?

[aadadams]

So these R51 V6 trucks have 4 cats right? If one or two go bad, can't we just put some plain piping in with a threaded bung for the O2 sensor? I mean instead of replacing the cats?

I need to replace mine too... I'll find out on Thursday what the damage is anticipated to be. I'd love to know if there are cheaper options that worked for others. I'm pretty handy, and I have a good set of tools... Any Magnaflow, Walker, or other 3rd party vendor success stories? Did you replace the front or rear or both?

[smj999smj]

Usually the rears aren't a problem; the fronts sorta "filter" the exhaust before it ever gets to the rears. Converters can fail in two ways: they become clogged/restrictive or they become inefficient at breaking down the emission gases. In either scenario, to properly fix it, the catalytic converter "should" be replaced. If a converter is after the rear oxygen sensor, it is not subject to "monitoring" by the ECM for efficiency. That means replacing it with a piece of pipe (or "test pipe," as it's sometimes called) will not cause the MIL to trigger and set a code. It might help performance but will also make the exhaust a little louder. On the R51, the front converters sit between the front and rear oxygen sensors, which means they ARE monitored for efficiency by the ECM. O2 sensors cycle from "rich" to "lean" on a constant basis. The ECM wants to see an approximate 2:1 ratio of cycling between the front and rear oxygen sensors. If the ratio is close to 1:1 ratio, the ECM can tell that the catalytic converter media has become inefficient at breaking down the exhaust gases, and sets a three-way catalyst code (P0420/430). Obviously, replacing the front converter with a "test pipe" will give the same results. An inefficient converter will not affect performance or driveability. Some people have, with some success, installed O2 sensor spacers (or made them from spark plug anti-foulers) on the rear oxygen sensors. This partially pulls the rear sensor element out of the exhaust stream and tricks the ECM and keeps it from setting the code. A clogged catalytic converter that is monitored should always be replaced with a new converter. As far as aftermarket vs. genuine Nissan, they are usually cheaper, but stick with a reputable, name-brand converter (ie Walker, Bosal, etc.). Some discount brand converters have been found to not up to OEM specs and the MIL will still set after you've installed it.

[aadadams]

As far as aftermarket vs. genuine Nissan, they are usually cheaper, but stick with a reputable, name-brand converter (ie Walker, Bosal, etc.). Some discount brand converters have been found to not up to OEM specs and the MIL will still set after you've installed it.

That's what I'm afraid of... I think I can do the job but I'd hate to end up having to go to the dealer anyway... I've read about Walker cats failing in a year or two... While some have mentioned the MagnaFlow cats no follow up reports have been given on their durability. I hope someone with firsthand knowledge of the situation offers viewpoints before I commit to a dealer repair...

[nutbar78]

I haven't had to replace mine yet, and from what smj999smj is saying, you can replace the rear cats with "test pipes" and be safe, so that a good thing. I had Meinike replace both cats on my Passat and she ran for fine for another 70K before I traded her for the PF. I think Meinike used Walker cats, but they didn't do the best job welding them in. There was an unexplained whistle that started after they were installed.

[smj999smj]

I've always had pretty good luck with Bosal exhaust and converters. Rockauto.com has the front converters by Bosal for $235 each. They also have Eastern Catalytic converters for a little less and Magnaflow OEM Grade for $342 each...all a lot better than the $600+ Nissan wants for them.

[disallow]

Don't forget to keep your old Catalytic converters and sell them to a scrap yard. The precious metals are worth a fair bit, and can help offset the cost of replacement. I'd venture to say somewhere in the neighborhood of $30-50.

[aadadams]

Wouldn't you know... Took the truck in this morning and I noticed on the way in that my service engine soon light was not on anymore. They changed the oil and checked for a code but could not find one related to the cats or otherwise. I'm not sure what to think. The last time I was there the ses light was on and they said that I had a code related to the cats, but they would need to check further to see what it was exactly... Oh well...

Not sure what to think, between the ses, vdc, and slip lights coming on and off for seemingly no reason and quite sporadically I'm growing weary...