Mazda Talk Forums

That's right, if the nut/stud won't separate then it is very tough to re-install them.

Anyone getting a P0420 CEL with the RS midpipe cat? I have this on my NB ('04) and after several months the CEL light came on. Changed the upstream sensor and ligth went away for about 4 months.

Checked at the dealer and said that the ECU doesn't recognize the cat. Sometimes it goes away on its on but come back after 100miles or so. The dealer said to ignore.

We have a regular issue on 1999 and 2000 year with failure of coils destroying the converters but VERY rare to hear of any issues on 2001 through 2005. I will assume you have checked to make sure the car is not running too rich (spark plug gap proper, good plug wires, clean air filter, good PCV valve, no soot evidence on muffler tip, etc). If all that checks out and you want to have factory inspect for insufficient catalyst contact us by email for details.

A potentially easy solution is try to back the second O2 sensor a little out of the stream of flow so it is a little less sensitive (do a google search for "antifouler trick" for the thousand websites that show you how to take this one dollar item from local autoparts store and use it to back second sensor out of the stream to avoid this code.

Following are good: Plug wires and air filter were replaced with ULTA and AEM respectively. Good PCV valve (no signs of wear or leak), no evidence of soot on muffler tip.

CEL first appeared with original plugs (mileage was around 30k). Thought that was the issue and replaced plugs. Will check plug gap.
Should I inspect for insufficient catalyst before resorting to the antifouler trick?

I also have the RS muffler. All parts were purchased here and very pleased with the service level.

Thanks.

The antifouler trick avoids the trouble of sending back the unit for inspection, so it might prove less effort and less downtime. But assuming you still have the factory midpipe to slot in there in the meantime, contact us by email for details on getting that back to the factory if you like.

Did the install yesterday. Question: the midpipe ships with a gasket. I am assuming that's for the midpipe/muffler connection. If you've already got a Q or roadstersport duals installed, then you've likely already got that gasket, right? I didn't use it. I'm in trouble if that gasket was for the header flange/midpipe connection.

Another beautiful piece of hardware is now on my car.

That's right, you end up with extra gasket.

I installed mine along with the Max Power ceramic header. A few things to pass along that may help. I had the same problem with the nuts/studs coming out as one and refusing to part. I have new ones on order...in the meantime as Brian suggests use bolts. These are M10 X 1.25 fine thread metric. Lowes had them in 50mm and 75mm lengths. I thought the 50s were too short so got 75s which were too long so I put over sized nuts as spacers between the bolt heads and washers.

Simple solution for routing the rear O2 cable (after I partially melted a connector) ...Unsnap the heat blanket using one of your forked plastic spatula-like panel removing tools (essential for working on any modern snap-together vehicle) and route the cable under (or on top of depending on your point of view) the heat shield from front to back...I hid the connector under it too.

If you are removing the OEM header you can use the spring brackets that held the O2 cables to that and attach them to various points under the car.

Notes on install with NC Automatic at THIS LINK

My 2000 came with donut gasket between the down pipe and mid pipe as well as mid pipe to muffler, I'm only using the gaskets that come with the midpipe and am having some leaks at both flanges. How do I correct this? I don't think the new gaskets fit with the old donuts in place.