Dylan5993

Hello, this is my first post here. I've been reading post after post trying to understand more about the catalytic converter and the complete exhuast system layout and how it works as ive been having some issues with my recently purchased car. Ill start from the beginning to the point I have reached today for better understanding.
I bought the car with stock everything so it's a 2006 Lexus IS250 2.5L V6 Engine with 156000kms on the clock. Upon changing the headlights to LED when I removed the air box. I mistakenly forgot to unclipped one last clip at the rear of the air box and gave it some force which snapped the plastic holding the clip in place.
I noticed the air filter seal was almost had it so I decided im going to replace the air filter. I bought a replacement K&N air filter and replaced it. (PN: 33-2452）I didn't worry about the missing clip as there was still 3 other clips on other sides and they gave it still a fairly air tight fit.
From purchasing the car whenever I WOT you would have a terrible smell coming from the exhuast egg like smell. I tested the different conditions that this smell would occur and decided to have a mechanic take a look. He stated there was no exhuast leak and the catalytic converters downstream were most likely gone bad. In Australia the laws are you cannot alter the exhuast system at all. My mechanic agreed to remove my catalytic converters downstream and strip them internally and reinstall so thats what I had done. About 2 days later when driving around I surely received the CEL with the VSC aswell. After doing some research I recently bought some o2 spacers and spaced out the downstream sensors out of the air stream hoping this would fix my CEL code issues. Until unfornately after driving today I received the same CEL codes of P0430 and P0420.
Since the removal of the cats the smell is not as bad but it is more of a constant Burnt Fuel smell even when standing next to the car. I've also noticed with the car idling the Fuel Economy is at max 30L/100kms. Unsure if thats normal or??

I've done constant researching on many forums. Looked at numerous intake and exhuast systems but im at a loss with it all. All I want is my exhuast system to smell a bit less eggy and the CEL Code to not come back on. I've seen numerous people warn away from Xforce exhuast systems. I've looked at Joe Z exhuast pts. My question is if I go for a catback exhuast full system. What happens with the o2 sensors. Wont the CEL come back on? My tank averages range from 12.L per 100kms now. As compared to 9L per 100 kms. Could it be the upstream sensors or cats? It's just unusual as it's only since the removal of the secondary cats.

Any forum links with more help, suggestions of what to try or look at, personal experiences, explainations, anything at all would be greatly appreciated. Im happy to spend some money to get this fixed once and for all.

ill attach some photos of few different things.






Thanks in advance ! !
- Dylan.

Ultra4

I might need to come back after a cup of coffee and re-read all that, but it sounds to me like all your issues will go away with a new set of cats and a couple cycles of decarbonizing. Decarb it first so you don't destroy the new cats.

Your downstream O2 sensors are doing their job and saying "hey, there's too many noxious things in here" and kicking the dummy light. There are "mini-cats" that you can thread in between the o2 sensor and the exhaust pipe to allow you to run full Greta pipes without the CEL, but I'd personally just get some aftermarket cats and pay a welder to swap the OEM ones. Not sure if replacing a malfunctioning emissions part with a functioning emissions part is legal, but that'd be my preferred fix.

Dylan5993

Thanks for your quick response, I assumed the o2 spacer wouldve fixed the cel light but guess it still has enough of a reading for It set it off. I would prefer to pay a bit extra to get a better exhuast if I could. Although the o2 sensors are before the rear catalytic converters. The only ones that my mechanic gutted are the downstream catalytic converters. Wouldn't replacing the downstream cats not affect the sensor due to it being before? Sorry just a bit confused.

If im mistaken and that's not how that works. I would prefer a new full exhuast (minus headers, they remain stock) would it be best to get a catback / axleback exhuast and " those mini cats" The main exhuast I could find was the xforce but I've heard bad reviews on here.

If my best and only option is to replace the downstream cats that will be the one I will do though. Just trying to see my options.

jizz4jazz

iTrader: (1)

Egg smell is the Flaps in behind the rear bumper being worn/gone. Theres a big thread on this.

Armadous1

Run an smoke leak test on the exhaust system.



Also here is the pathways to check for your trouble codes. I am a lexus technician so my memory is pretty good for these cars but if I missed something someone please add. P0420 The oxygen storage capacity value is less than the standard value under active air-fuel ratio control (2 tip detection logic) Gas leak from exhaust systemAir fuel ratio sensor (bank 1 sensor 1)Heated oxygen sensor (bank 1 sensor 2)Exhaust manifold sub-assembly RH (TWC: Front catalyst)Front exhaust pipe assembly (TWC: Rear catalyst)

P0430 The oxygen storage capacity value is less than the standard value under active air-fuel ratio control (2 tip detection logic) Gas leak from exhaust systemAir fuel ratio sensor (bank 2 sensor 1)Heated oxygen sensor (bank 2 sensor 2)Exhaust manifold sub-assembly LH (TWC: Front catalyst)Front exhaust pipe assembly (TWC: Rear catalyst)



ENABLING CONDITIONS whenever following DTCs are not present P0031, 32, 51, 52 (A/F Sensor heater - Sensor 1) P0037, 38, 58, 59 (O2 Sensor heater - Sensor 2) P0100 - P0103 (MAF meter) P0115 - P0118 (ECT sensor) P0120 - P0223, P2135 (TP sensor) P0125 (Insufficient ECT for Closed Loop) P0136, P0156(O2 Sensor - Sensor 2) P0171, P0172, P0174, P0175 (Fuel system) P0300 - P0304 (Misfire) P0335 (CKP sensor) P0340 (CMP sensor) P0351 - P0354 (Igniter) P0500 (VSS) P2196, P2198 (A/F Sensor - rationality) P2A00, P2A03 (A/F Sensor - slow response) Battery voltage 11 V or more IAT -10°C (14°F) or more ECT 75°C (167°F) or more Atmospheric pressure coefficient 0.75 or more Idle OFF Engine RPM Less than 4,000 rpm Fuel system status Closed loop A/F sensor Activated Engine load 10 to 70 % All of the following conditions 1, 2 and 3 are met: 1. MAF 5 to 45 g/sec. 2. Front catalyst temperature (estimated) 600 to 840°C (1,112 to 1,544°F) 3. Rear catalyst temperature (estimated) 600 to 840°C (1,112 to 1,544°F) EVAP system monitor The monitor has not run yet or the vacuum introduction has been completed. A/F sensor monitor Completed Rear HO2S monitor Completed Shift position 4th or higher



TYPICAL MALFUNCTION THRESHOLDSOSC (Oxygen Storage Capacity) of Catalyst Less than 0.078 g

Tomcat0347

Sorry tried looking everywhere here, just wanted to know how many catalytic converters does 2006 Lexus is250 have? Is it 4? How can one tell which one is not working propertly?

tbear

On my 2010 AWD there are four. Two primary as part of the exhaust manifold and two secondary ones located towards the rear of the exhaust.

My car is displaying symptoms of having the cats clogged (no power and sulphur smell when climbing hills) so I'm taking mine to a muffler shop next week. I'm hoping they can weld in an aftermarket cat into the manifolds.

06Is2filthy

This is hugely helpful once I figure it all out.
In my car, the p0420 turns on and off seemingly related to how much fuel I have. There’s no pattern other than the check engine lights sometimes turn off after I fill the tank only to turn on randomly a tank or two later. I only use gas from a station I trust and my driving pattern is pretty consistent.
I’m going to run some tests on my cats and stuff to make sure it’s not something obvious but any input would be great.
This is the most information I’ve found sans repair manual thank you.