P0420 CEL 99 civic si

[Bruce Leroy]

spark plug defouler FTW...

There are so many threads being created about defoulers, it would be nice to compile everything into a single thread with the hopes that it could become a sticky. I will attempt to do so, addressing issues relevant to those using a race header.

Rationale for defoulers, this from Pro Street:
On ODB-II vehicles (96+), the ECU has two O2 sensors for diagnostic purposes. The first O2 sensor is located before the Catalytic Converter. This O2 sensor is responsible for all the Air/Fuel tuning and is imperative to the operation of the vehicle.

The second O2 sensor is located after the Catalytic Converter. The whole purpose of this O2 sensor is to ensure that there is a functioning catalytic converter in the system. The way it can detect this is to make sure that there is a difference in exhaust gasses between the first O2 sensor and the second. If the same exhaust reading is detected, then the ECU knows that there is either a damaged Catalytic Converter or no Catalytic Converter at all.

The ECU will then trigger a Check-Engine Light. On some instances, the vehicle will be thrown into a "Null" mode where the vehicle will not go over a certain speed and will be basically rendered useless.

This mechanical O2 fix is basically a way to space out the O2 sensor so that it still reads SOME exhaust gasses but it removes the O2 sensor from the direct flow of the gasses as to make the ECU believe there is a restriction in the exhaust gasses such as by a Catalyst.

From E46fanatics:
WHO: People who upgraded to aftermarket headers without installing any catalytic converter will get a catalytic inefficiency error code. Likewise, people who install high-flow catalytic converter will get the same "inefficiency" error codes.

WHAT: Catalytic Inefficiency codes on the post cat 0xygen sensor: P0420 (cylinder 1-3) P0422 (cylinder 4-6).
Ref: http://www.obd-codes.com/trouble_cod...old-bank-1.php

WHY: The reason why your OBD-II diagnostic systems report this error code is because the 02 sensors detect an above normal exhaust reading when compare to OEM catalytic converter. The OEM catalytic converter does an excellent job at filtering/cleaning/converting exhaust fumes into cleaner air. The DME/ECU calibrates its post-cat sensors to the OEM catalytic converter performance and specs. Therefore, aftermarket cats do not clean well enough to satisfy the catalytic efficiency monitoring of the DME. This is a very common problem with aftermarket cats especially the high-flow ones.
An "inefficiency" reading does not mean that your catalytic converter is broken especially if it is brand new. Again, the error codes just means that they are not performing as efficient enough to meet OEM standards.

SOLUTION: There are three feasible options to solve this inefficiency problem

Ignore.
Spark Plug non-fouler (aka Spark Plug defouler)
Software upgrade

-Ignore-Since the post catalytic converter oxygen sensors is purely for emission monitoring it does not in ANY way affect your fuel trim and car performance. Therefore, it is perfectly fine to ignore the check engine light.
-PRO: No time and resources wasted on fixing problem
-CON: Annoying check engine light

-Software Upgrade-Software upgrade from major tuning companies will flash your DME to remove the "catalytic efficiency" monitoring feature.
-PRO: Fast and requires no hardware/equipment modification to exhaust systems
-CON: Expensive

-Spark Plug non-fouler (aka Spark Plug defouler)-By installing the spark plug non-fouler, you are in essence moving the rear 02 sensor out of the direct flow of the exhaust stream/flow. By doing so, you are tricking the 02 sensor will an inaccurate reading. Since the 02 sensors is not directly in the path of the exhaust fumes, it can not accurate measure the exhaust fumes.
-PRO- Inexpensive
-CON- None

Types of defoulers:
1. Angled. As the name suggests, the defouler is angled at 90 degrees, which allows for greater clearance. This is especially important on Vibrant and BuddyClub headers.



2. Straight. These are straight, which seems fine with DCSports race headers, but not the Vibrant and Buddy Club.



DIY defoulers: There have been a number of threads about making your own defouler.

http://www.8thcivic.com/forums/bolt-...-defouler.html

solution: Check engine light w/ aftermarket Headers - E46Fanatics

Installation:



All defouler threads on 8th Gen:

http://www.8thcivic.com/forums/searc...archid=2352001

Where to buy:

eBay Motors: O2 sensor angle header WRX STI EVO 350z Civic SI tC RSX (item 250268957202 end time Jul-19-08 21:27:57 PDT)

This guy does stuff for VW's: [email protected] e-mail him with your request.

[email protected]

Mechanical 02 Simulators

A&J Racing :: Intake & Exhaust :: T1R O2 Fix

BLOX Racing Check Engine Light Eliminator - BLOX Exhaust Parts

Universal - Cel Eliminator 963-111-101 >> Weapon R Cel Eliminator

King Motorsports Unlimited, Inc.

Defcon Products : Oxygen Sensor Simulators

Hope this helps everyone out. We want this info to be disseminated to as many people as possible who either have race headers or are considering them.

Please post any extra info you have that would benefit fellow members here on the forum.