2011 is250 catalytic converter issue

[bixtape]

Hi people . After one year of owning my baby I finally discovered this forum lol. 

My lexus is currently 95k miles .4-5 months ago , I got the back boxes removed. The guy who welded the end pipes did an absolute **** and been running with a lot of leaks around the welds. 1-2 months after the delete I started sensing rotten eggs smell and followed by that the all mighty check engine light. 

I've changed the spark plugs thinking that could be the issue ( didn't help ) the smell is still there , even though it's not as bad as before , however the check engine light comes up a lot often now and goes a way after a day or 2. ( see below pic with the error code)

My question is - is there any chance the o2 going bad or it's defo the cats? I will be redoing the Backbox delete at some point to have proper welds done by someone who knows how to do it but if the cats need changing , this will wait a bit. 

Also to add another symptom - the car revs about 500 rpm higher for a sec when I'm taking off (does that only when very lightly accelerating) . When I had the spark plugs removed , we checked with the mechanic the throttle body and it seemed absolutely fine , no corrosion or any issues. 

Has anyone encountered this with his 250 at this mileage ? I've found some dodgy website which sells the cats for £350 , does that sound right to you guys? 

Has anyone sold their cats for recycle in the north east? 

 

 

[Linas.P]

O2 faults can 100% be caused by leaks in exhaust... So definitely fix any leaks before spending money on cats or sensors. 

So the way I see it - leak causes wrong O2 reading > wrong O2 reading inevitably causes cat fault code. Now sure - it could be that O2 sensor itself is bad and that will also cause cat not to function properly (because remember - the only reason for O2 sensor to exist is to monitor cat function, and "below threshold" that means o2 sensor reading is wrong), or it could be just a leak... or it could be cat. I mean it is not impossible that cat (1 of 4) has failed after 100k miles. However, the way to diagnose would be to first ensure there are no leaks, then check the sensor and only then start thinking about the cat.  

[bixtape]

39 minutes ago, Linas.P said:

O2 faults can 100% be caused by leaks in exhaust... So definitely fix any leaks before spending money on cats or sensors. 

So the way I see it - leak causes wrong O2 reading > wrong O2 reading inevitably causes cat fault code. Now sure - it could be that O2 sensor itself is bad and that will also cause cat not to function properly (because remember - the only reason for O2 sensor to exist is to monitor cat function, and "below threshold" that means o2 sensor reading is wrong), or it could be just a leak... or it could be cat. I mean it is not impossible that cat (1 of 4) has failed after 100k miles. However, the way to diagnose would be to first ensure there are no leaks, then check the sensor and only then start thinking about the cat

What you are saying makes a lot of sense. I will start with the exhaust pipes in this case and have them welded properly. I forgot to mention 1 thing - that egg smell when flooring actually seems to have disappeared. I've used an redex petrol fuel system cleaner and it seems to be working. I did 1 shot 3-4 months ago with no luck , but a week ago I did second one and I've gone through couple of tanks and now the smell seems to be gone. This was recommended by some fella with a gs who had the same smell and it was gone after 2 shots of the liquid . Thank you for the help pal!

[Linas.P]

Smell itself could be due to bad reading.. ECU get's wrong reading, send wrong air/fuel ratio, for example when engine is cold ECU uses richer mix to heat-up cats, but if reading is wrong it may be dumping fuel all the time (perhaps related to your higher than normal revs)... cat does not work optimally and you get smell... The way to further diagnose this would be to look at "live data" e.g. if you have bad sensor it would likely show like just stable 14V or 0V (open or short circuit, whereas normal would be fluctuating ~1V). So for example if issue is caused by the leak, you would see O2 sensor output fluctuating as you rev the engine, but in wrong range... whereas if it is dead, then it will simply going to be stuck to most likely 0V.

Anyway - I am speculating a lot here... In short what I am trying to say - smell may indicate that cat isn't working efficiently, but not necessary that it is actually bad. It may not work efficiently due to many reasons. 

I am quite surprised it shows C1201 (which is comms error), nasty to diagnose on it's own, but sometimes shows it's ugly face together with other codes like for example bad O2 sensor... so most likely will disappear when you fix P0420.

The other funny code is B1421... it just means when you were reading codes car was inside the garage or it was dark, so ambient light sensor gives a fault code for that... very picky... if you shine the shop light at the sensor the code would dissapear 😄

Good luck with the fix and let's us know how it went...

[bixtape]

10 hours ago, Linas.P said:

Smell itself could be due to bad reading.. ECU get's wrong reading, send wrong air/fuel ratio, for example when engine is cold ECU uses richer mix to heat-up cats, but if reading is wrong it may be dumping fuel all the time (perhaps related to your higher than normal revs)... cat does not work optimally and you get smell... The way to further diagnose this would be to look at "live data" e.g. if you have bad sensor it would likely show like just stable 14V or 0V (open or short circuit, whereas normal would be fluctuating ~1V). So for example if issue is caused by the leak, you would see O2 sensor output fluctuating as you rev the engine, but in wrong range... whereas if it is dead, then it will simply going to be stuck to most likely 0V.

Anyway - I am speculating a lot here... In short what I am trying to say - smell may indicate that cat isn't working efficiently, but not necessary that it is actually bad. It may not work efficiently due to many reasons. 

I am quite surprised it shows C1201 (which is comms error), nasty to diagnose on it's own, but sometimes shows it's ugly face together with other codes like for example bad O2 sensor... so most likely will disappear when you fix P0420.

The other funny code is B1421... it just means when you were reading codes car was inside the garage or it was dark, so ambient light sensor gives a fault code for that... very picky... if you shine the shop light at the sensor the code would dissapear 😄

Good luck with the fix and let's us know how it went...

I found a guy who does decent welds and I'm going to visit him today to have a look at the exhaust pipes and figure out how we will go about the redoing the backbox delete. I will keep you guys updated 👌

[bixtape]

13 hours ago, Linas.P said:

Smell itself could be due to bad reading.. ECU get's wrong reading, send wrong air/fuel ratio, for example when engine is cold ECU uses richer mix to heat-up cats, but if reading is wrong it may be dumping fuel all the time (perhaps related to your higher than normal revs)... cat does not work optimally and you get smell... The way to further diagnose this would be to look at "live data" e.g. if you have bad sensor it would likely show like just stable 14V or 0V (open or short circuit, whereas normal would be fluctuating ~1V). So for example if issue is caused by the leak, you would see O2 sensor output fluctuating as you rev the engine, but in wrong range... whereas if it is dead, then it will simply going to be stuck to most likely 0V.

Anyway - I am speculating a lot here... In short what I am trying to say - smell may indicate that cat isn't working efficiently, but not necessary that it is actually bad. It may not work efficiently due to many reasons. 

I am quite surprised it shows C1201 (which is comms error), nasty to diagnose on it's own, but sometimes shows it's ugly face together with other codes like for example bad O2 sensor... so most likely will disappear when you fix P0420.

The other funny code is B1421... it just means when you were reading codes car was inside the garage or it was dark, so ambient light sensor gives a fault code for that... very picky... if you shine the shop light at the sensor the code would dissapear 😄

Good luck with the fix and let's us know how it went...

Mate I've been researching and asking people around for a while and no one has been more spot on than you .  

I went to this guy who I met on fb car meets page. We will be redoing the backbox delete properly this time and what's more important is that he did diagnostics on the car and what did we see there?? Both o2 sensors at 0v when reving the engine!!!! Did a reset on them and now they are working fine as they should!!!!!!! The car shifts as it should now , there's no sudden 500 rpm rev when lightly accelerating !!!!!!!!! 

After the backbox delete I will drive around and continue keeping an eye on this and will update this thread. There's so little info in the uk when you get a poor backbox delete which causes you so much trouble specifically for these models!!!

Thanks again  mate !

[Linas.P]

Happy to hear it helped!

[MrTrendizzle]

On 4/18/2023 at 12:05 PM, bixtape said:

After the backbox delete

Have you just cut the rear boxes off and replaced with straight pipe?
If you have a friend that can weld now, then i suggest you get the stock exhausts, have your friend cut along the side seem and put the straight pipe inside, weld it back up and you're golden. This will prevent you getting done by DVSA or the police and stop MOT issues as "it looks stock" The bonus being if it's too loud or you're losing too much pressure, you can open it back up, drill a few holes in the pipe and pack in some fibreglass packing to lower the volume a little and or create some back pressure.

I did this on my RX8 a few years back and while my friends all got stopped and given 7 days to re-mot their car i was let on my way as my exhaust was "standard" even tho it was loud. I just claimed i had removed the center box.  

 

[Linas.P]

The backboxes are unregulated, as long as vehicle passes emissions and is not too load. The noise testing is as well quite complicated, so I doubt police could do much about it as none of them would have right equipment to test. So  don't touch any emissions parts (like cats and dpf) and it should be fine.

In short - it doesn't need to be stock and DVSA or Police should not be concerned about backboxes. 

[bixtape]

On 4/23/2023 at 10:02 PM, MrTrendizzle said:

Have you just cut the rear boxes off and replaced with straight pipe?
If you have a friend that can weld now, then i suggest you get the stock exhausts, have your friend cut along the side seem and put the straight pipe inside, weld it back up and you're golden. This will prevent you getting done by DVSA or the police and stop MOT issues as "it looks stock" The bonus being if it's too loud or you're losing too much pressure, you can open it back up, drill a few holes in the pipe and pack in some fibreglass packing to lower the volume a little and or create some back pressure.

I did this on my RX8 a few years back and while my friends all got stopped and given 7 days to re-mot their car i was let on my way as my exhaust was "standard" even tho it was loud. I just claimed i had removed the center box.  

 

This sounds good to be honest. I've been stopped by the police for being naughty naughty , however never said anything about the exhaust. No issues whatsoever pal 👌 I guess it's not too loud as realistically on normal cruising u can't even hear it. 

Also I've checked with my garage about the mot and was told we all good it will pass without any issues

[bixtape]

Hello guys long time no see . I haven't updated the thread but the time has now come and I'm financially ready to spend more money on this car 😂 

I've finally received 2 denso downstream sensors to replace them with the hope to fix this whole issue . HOWEVER , due to me being fixated on the exhausts i've overlooked the pipes around the o2 sensors and have now found a leak before bank 2 and now everything adds up. The situation is not looking good . I didn't proceed with changing the o2 sensors as per my discussion with the legend @Linas.P there's no point doing so since there's a leak and also who knows how much metal Is actually left in the area.

I think the story gets even more complicated in a way now than before and I really need help your help guys

Here are pictures showing the flances at bank 2 . It is clear that new cats are needed but what worries me if I'm going to be able to attach these new cats to the old flances? 

Considering how bad the welders in my area are , I don't think there's a point for considering of fixing the exhaust leak ? 

How should I go about this ? 

 

[bixtape]

I hope you can see the pictures through this link as for some reason I couldn't upload them directly onto the thread 

https://ibb.co/sWh0hjg

https://ibb.co/DYfXj4q

https://ibb.co/dLVCWpm

https://ibb.co/VpRgB4m

https://ibb.co/k5yX14J

[Linas.P]

Ahhh yeah... flanges and rust under heat shields... This is how every 15 years old Lexus looks like underneath. Literally had same thing fixed 2 weeks ago as my car failed mot on lamda (basically leak in exhaust).

In my case I was lucky as they were still able to weld the holes under the heat shields, but my flanges were even worse. I had an option of £200x2 for new flanges to be put in and wait for a week, or have straight pipe welded there... I went with the pipe, but for next mot looking to get whole new exhaust, desperately need mid section as pathing is just temporary, so will get that done maybe in the spring and and fit flanges to accept new mid-pipe. So for time being it was £40x2 for flanges fix and £40 for patching few holes. 

Lucky for me I have found the guy around me who seems to know how to weld and was very fair with pricing and advice. Sadly don't have pictures of how it looks under the heat shields, but in principle it is rusty pipe with some spot welds on it. As well we just removed the heatshields and discarded them, basically major part of the issue are the heatshields themselves as the dirt gets in the them and accelerates the rusting. 

[bixtape]

Wow man I'm so glad exactly you have the same issue like me and I'm saying this in the nicest possible way 😂😂 

I've been thinking about this and decided that if welding can fix this issue I would travel , before you said this lol 

You are the guy who i trust the most to be honest , what would you suggest is the best way to go in my case ? I've got a friend of a friend who's a really good welder however he's 5 hours away from me , but if welding will resolve the issue properly then welding it is . I think either ways the flange at the downpipe needs to be dealt with , even if I get new cats , I'm sure that old rusty flange will cause a leak in future ....

[Linas.P]

This is not only me that having this issue - for normal mild-steel exhaust you looking at 8-12 years of lifetime, stainless steel is more like 30 years. So everyone will have similar issues with exhaust by now.

As for welding on rusted pipes - it is 50/50, because exhaust is usually rusting from inside, so it is very hard to tell from pictures if welds will work or not i.e. if pipe is too thin to weld, it will just blow through and results in what welders refers as "chasing the hole/weld". Basically as the hole get's filled with weld the heat from molten metal melts another hole just to the side of it. Experienced welders can adjust the welding machine to match the metal thickness and minimise the blow trough, but sometimes it get's to the point where metal is simply too thin to weld on.

Either way - welding on rusted pipes is temporary fix, you will get holes next to the welds within 3-6months, but as the case of say passing MOT whilst looking for suitable replacement it works. In my case pipe on either side of the flange was quite solid, so the repair in the picture above could be considered semi-permanent. However, I have rust just behind O2 sensor, specifically under those heatshields and there metal is very thin already, so I am sure I will have exact same problem very soon. In fact 3 weeks later I already can hear a little hole somewhere.

So the answer is - if you looking for temporary repair, then I suggest welding it. But if you looking for repair that lasts, then you will have to replace central section of exhaust. In my case I am looking to replace whole exhaust maybe in spring, but I just bought myself some time over the winter to find what I want. 

[bixtape]

I am in no rush so I'm going to repair the whole issue , I'm not giving up on this baby , I've put quite a lot in it and been taking care of it ( apart of trusting wannabe welders ) and not planning on changing the car in the next at least 2 more years. ( 2 years , and 25k miles so far ) 

By changing the whole exhaust system do you mean the headers too ? So I'm going to do my research to replace the cats that have the exhaust leak with brand new ones , but changing the headers too , isn't that a massive pain in the ***** getting to it and also quite expensive ? 

By the end of the month I should've ordered the cats but I doubt I would be able to deal with the flange on the side of the headers... It will have to be following month most likely....

[Mr Vlad]

Hi Alex. WOW that exhaust looks wrecked with rust. If you can afford it then go straight to a replacement exhaust system. No need to change the headers as they're made of better metal. 

You say you've bought O2 sensors already. Are they genuine or none OE? Why I ask is because where O2 sensors are concerned Genuine is the Only way to go. None genuine work for a bit then pack up. Got that info from a local specialist who works with them.

[Linas.P]

No - I will leave headers as they are, it would be nice to replace them, but it is indeed major cost and massive pain. I was considering to maybe take them off and get them cleaned (like sand blasted and cera-coated, but I believe even that would be in £300-500 range).

So by "whole" exhaust I mean just central and rear sections and leaving headers alone. My rear section is actually quite new, so I perhaps keep it or sell it, but because I will need to replace entire central section anyway and I want to replace rear silencers as well the extra 2m of piping will be minor cost in grand scheme of things. I am looking at ~£700 to replace central and rear section to the stainless steel.   

15 minutes ago, Mr Vlad said:

Hi Alex. WOW that exhaust looks wrecked with rust. If you can afford it then go straight to a replacement exhaust system. No need to change the headers as they're made of better metal. 

You say you've bought O2 sensors already. Are they genuine or none OE? Why I ask is because where O2 sensors are concerned Genuine is the Only way to go. None genuine work for a bit then pack up. Got that info from a local specialist who works with them.

I can as well confirm that from my own experience. The unbranded sensors works for few mounts, if you very lucky for a year and fail. My worst so far failed in 2 weeks for me. O2 sensors are slightly better than Lambda, but still they don't last. By that I mean - 50% of non branded Lamda does not work straight from the box (i.e. you instantly get some sort of code for Lambda, too lean, too rich, low voltage etc.), O2 sensors mostly work out of the box, but they fail fairly quickly and you get codes for cat-performance. 

So the best solution is to use either OE (i.e. Toyota branded made by Denso) or OEM sensors from Denso. The risk here is only that both Toyota and Denso marked sensors are often fake in place like eBay or amazon, so to get real genuine sensor one may need to go directly to Lexus and they are expensive.

[bixtape]

Yes vlad , I've went with denso from rock auto with the advice from linas , he's been super helpful so I'm taking the right decisions now hahaha

So that exhaust system gotta be like custom or... ? Is there like a reputable website for our 250s where we can just get them from ? Or welding needs to be involved too?

[Linas.P]

7 minutes ago, bixtape said:

Yes vlad , I've went with denso from rock auto with the advice from linas , he's been super helpful so I'm taking the right decisions now hahaha

So that exhaust system gotta be like custom or... ? Is there like a reputable website for our 250s where we can just get them from ? Or welding needs to be involved too?

Yes - that will be custom... the guy who welded my exhaust is happy to do it and to be fair most of the cost will be the parts themselves - silencers ~£100x2, replacement SS-Cats £120x2, so that is £440 just in parts, meaning £260 for work and stainless steel piping. That is really cheap.

The only thing we don't agree with so far is that he "does not want to take money"! Basically, he told me I am wasting money on full dual exhaust, because I want to fit X-Pipe instead of Y-Pipe and have two separate pipes going to the rear. He said that is basically going to make no difference and he advises me not to do it. 

So really we just agreed that I will think about it and comeback later... but realistically we just talking about either £700 and keep it as Y-Pipe after secondary cats, or £800 and do X-pipe and make two pipes going back instead of one. Resonator will go either way. 

[bixtape]

@Linas.PMy rear "exhausts /pipes" are new , i went to a guy who did it kind of properly ( still small leaks at the welds where the backboxes were , but this time much better...) 

if ive understood right you are going custom stainless steel for the centre and rear done by a shop right ? I know a reputable place close to me but I was quoted for a backbox delete £700 + and without the tips , so I'm crossing out this shop for sure . I'm just wondering if there are already complete exhaust systems ready to be purchased from a reputable website ? Or it needs to be custom as the shop needs to deal with the flanges too?

Edit: just read your reply after I posted this. 

Should I just freaking buy all the pipes needed to do the custom exhaust system and do a small trip of 5 hours to my pal who I trust the most and know I won't get ripped off or mess it up ( he's a welder for redbull haha ) 

[Linas.P]

The only place I know who advertise themselves as selling complete system is Tony Banks Exhaust in Leeds. However, they are "custom exhaust" shop by definition... so realistically custom exhaust is the only way to go. I am no aware of anyone selling central section and basically shipping it out... almost all the shops that offer central section will require to bring the car to their place and they will make the exhaust on the car, which is the definition of "custom" exhaust in my books. 

My understanding is that Tony Banks would do IS central section for ~£700 and they charge ~£300 for rear and that is what custom exhaust for IS usually costs. Doing it together in one go probably would be slightly cheaper i.e. £800-850. They have not named the price, but they alluded to that over the phone. 

[bixtape]

I understand now Linas , thank you for clarifying this , I've never dealt with this or had to research so I was quite clueless , but I got it now haha.

Thank you so much for your input

I know what the plan is , now I just gotta do my research for shops and not get ripped off , thank you .

I will update this thread again once I've got progress with this and will probably summarize the whole issue at the end so the next newbie like me finds it as helpful as possible !