Good Morning All,

Last weekend the g/f took her Z down a dirt road, managing to scrape bottom twice. Plugging the car into a code reader, it tells me the "Catalyst System Efficiency Below Threshold Bank 2". I am wondering if the converter itself is damaged, or if damage to the pipe upstream could cause this reading. Right now it is very difficult to get under the car to check.

Assuming it is the converter, how hard are they to replace? Is it a bolt in or weld on operation?

The converters are rather pricey when purchased new. There is a salvage yard nearby with a couple of converters. What is the wisdom of using used converters?

Thanks all for the help!
Jeff

 

First thing would be to get under the car to see if the cat is actually cracked or whether the 02 sensor was just damaged. If it is the 02 sensor, get the socket for it (don't remember off hand the size - maybe 22m, but it has a notch for the wire) and change it out with OEM after letting PB blaster or something similar soak in.

Cats are pretty easy to replace as long as you don't have rust issues and you have the right combination of sockets, flex joints, and extensions. Here's a write-up for install test pipes, but the procedure is the same if you're simply swapping cats. They bolt on. No welding required. https://my350z.com/forum/intake-exha...ation-diy.html

 

^ Like HTID said, check if it's the cat itself or just the o2 sensor. The harnesses for both the downstream sensors sit on a bracket bolted to the bottom of the transmission, so it's definitely possible something reached up and snagged the wiring. If it is the cats, they're pretty easy to replace assuming you don't have rust issues (again, like HTID said). I've had luck spraying the bottom bolts (fairly accessible with the car on the ground) with PB Blaster the day before you do the work when the exhaust is cold, then again when it's warm/hot. The top bolts shouldn't need too much help since they're pretty well shielded from the elements.

Good Luck!

 

Found an old pic from when I changed my clutch a few years back. You can see the white wires that connect the 02 sensors to the bracket on the bottom of the trans. This is what Sparta was talking about. It would be pretty easy for something to snag it and cause the connection to be loose.

 

Thank you everyone for the responses. I am glad to say I think it was a false alarm. By coincidence, the #5 ignition coil has gone out as well. The car was showing a code for this along with the converter, but I did not connect the two until after I posted.

Once I replaced the ignition coil, the code for the coil and the converter disappeared. I can only conjecture the unburned fuel and air from the #5 cylinder hitting the converter was triggering the code. Of course, fixing the coil seems to have triggered a new problem, but I will cover that in a separate post.

Again, thanks for the great responses. You guys are great.

Jeff

 

Nothing like driving on an f'd up road in a vehicle meant for smooth pavement to reveal an issue which would otherwise present itself at a later date. Pretty sure my diff bushing popped after having done the same thing.