QR25DE Precat and Butterfly Screw FAQ

[Jake_reps337]

The first or the upstream O2 sensors are used to control the air/fuel mixture. if you put a ghetto sim on it you should be in limp mode now.

[hainesx]

OMG! I am so glad I found this post before racking up some miles on my Sentra. Since this thread was posted several years ago, I wanted to find out if anyone here has a 2006 that has experienced the butterfly screw problem. I assume that Nissan fixed the problem, but if even one person lost a screw, I'm pulling the intake tomorrow.

Also planning to install a header soon. They don't test emissions in my town, so not likely I will run into legal problems. I've read on this and other sites that the over-sensitive knock sensor can give false readings with the header upgrade, causing more vibration. Has anyone else experienced this? Is there a less sensitive knock sensor that can be installed instead of completely disabling the factory one and losing that protective feature? Thanks all.

[spse-r]

Hi all. new here. My '03 se-r is a daily driver with no delusions of grandeur. I've got a cracked stock exhaust manifold and no signs (knock on wood) of precat failure yet (maybe cause it has seen 4000 rpm like 3 times since I bought it from a teenage girl)

Anyone have any experience with the magnaflow header with the cat in it? I'm in Ga outside emissions area (only Atlanta tests), but would like to be able to sell it if I must.

Is it better just to go 4-1 and rig the O2? Do you lose low-end torque with that header?

[i68k]

with 4-1 and spaced o2 you will get more torque, since there wont be a cat there. you still have a cat on your midpipe, which should pass emission test. no sure how ga tests tho

[Amuse]

Originally Posted by Dangling Fury

So what can I do about it?

1. Remove the precat from the stock exhaust manifold (don't worry, you still have another cat in the midpipe). Take the exhaust manifold off the engine and use a long screwdriver to break the precat into pieces and completely remove it, you're going to have to do this from the bottom of the manifold, it's the only way to access the precat. Once all the big pieces are out, scrape the sides to make sure all the small pieces are gone and use an air blower to ensure all particles are removed. Make sure you wear a 3M surgical mask the entire time so you don't breathe in any catalyst dust.

When I remove the precat to clean it all out, do I replace the original screens in there before reinstalling or do I throw those out as well? So it will be all hollow in there when I reinstall it?

Also, do I need any ghetto sim or anything if I clean out the pre-cat and reinstall it?

[i68k]

you clean out everything, all hollow

you need 2 anti-foulers on the lower o2 sensor
so you dont get a p0420 cat code

[Michael48]

Here is a picture of what fell out of the top of my cat after it was removed. Added a AAA battery for size reference.



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Just a little more incentive to send your cats to the pound.

[uncledude]

All the advice is recieved and processed.
I'm thinking to spend $$$ on body/paint/suspension. With exhaust improvements.

I want a sweet driver.

I'm also considering repainting the V another color, mines black. Moon yellow pastel/flat finish is my first choice..

[04specVdiver]

Thank you so much for this read, I'm going to make sure to keep this spec V on the road longer thanks to this thread!


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[DynamiteShikoku]

I am checking out a SE-R Spec V tomorrow with about 150K miles, he's second owner so i am hoping it was not ran hard by either him or the original owner. Crossing my fingers about the pre-cat (such a stupid design to adopt). I am a previous B15 GXE owner and just recently is now totaled; so now i am upgrading

Other than removing the valve cover/removing the precat, is there any way that i can check to see if the precat has any damage to it or the cylinder walls?

[spraytech]

I recently purchased an 04 spec v. I'm the second owner of car and the original owner never serviced any of the factory recalls. My car is well past warranty w/120k but is it still qualify for the precat recalls? I plan on calling dealership soon but wanted some insight and see if others are in the sane boat as me. My car is completely stock.

[i68k]

sorry to say, but the precat failures are not recalls. there maybe some tsb for them, but its not a recall so the dealer will not fix this issue without charging you. make sure youre not burning oil, or losing coolant, then get yourself a catless header if all is well.

[spraytech]

So I was driving car yesterday and heard a loud pop followed by an awful sound like I had blown s hole in exhaust. Turns out that where the sensor plugs into precat blew completely off. Im guessing the precat wasnt letting the car breathe enough so the pressure built up and that sensor was its only escape. Anyway took off stock header and precat, then used hammer and screwdriver to scrape out the precat. Had to weld the sensor sleeve back on precat then reinstalled everything. Car is running a lot better now and has an aftermarket exhaust sound. It seems like performance is up a bit now that the car can breathe. Didn't throw any codes either so no check engine light.

On a side not I had to take off alternator to get that header bolt and took about 4.5 hrs including the welding to sleeve.

[i68k]

ouch, sorry to hear. havent heard anyone blow an o2 bung off without boost. im guessing your precat was really clogged up! you also should still have a cat on your midpipe, the pipe connecting to the header. hopefully you used new gaskets when reinstalling, as the donut gasket gets crushed into place and cant be reused, where the spring bolts are. just make sure youre not leaking there, as it maybe loud from exhaust leaks.

[spraytech]

No leaks on exhaust i68k. I did reuse the old gaskets though. I'm planning on getting Megan header and new exhaust in near future. Now that the precat has been removed is there really a need for new header though? Will I gain performance over the stock? If not place to discuss please pm me

Now that I think about it the only gasket there was a round flat on one side pointed on other where the spring screws connected. Did I miss something Lol it was late last night