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 Posted: Wed Dec 11th, 2019 09:54 pm
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Umpa
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Mana: 
I hope so, but I will buy a full upper gasket set, and new cat.  Will fit in summer 2020, and report on what happens.

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 Posted: Wed Dec 11th, 2019 07:39 pm
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Paul S
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Mana: 
been told the cat reduces the CO% by approx 0.30%, & dont figure a co% value of 0.60 is anywhere near enough to cause a cat meltdown, hopefully may just be fair wear & tear as in just needs a cat
:)

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 Posted: Wed Dec 11th, 2019 06:02 pm
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Umpa
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markt wrote: hi
if the rear lambda starts to switch at the same rate as the front one then yes it looks likely its a faulty cat,especially if the rest of youre readings are within spec.
Yeah, you have already said that..  I think there is an underlying cause though. 

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 Posted: Wed Dec 11th, 2019 09:21 am
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markt
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Mana: 
hi
if the rear lambda starts to switch at the same rate as the front one then yes it looks likely its a faulty cat,especially if the rest of youre readings are within spec.

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 Posted: Tue Dec 10th, 2019 08:15 pm
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Umpa
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Paul S wrote: dont know answer to that, except your motor failed its MOT with a high CO% of 0.60 The output from the cat is around 100c lower than the input..so when you remove it your be able to view the honeycomb core & see if its intact..it all helps. thought you replaced the O2 sensor?. & on that one be sure its an OE equivalent sensor like bosch or ngk, some of the non oe aftermarket parts dont work to the same tolerances as the oe stuff.Yeah replaced the upstream O2 sensor, but I don't think it was an OEM, but was for the car and had the correct connector.
I ask about the upstream waveform because I saw a video on youtube where he revved the car, and the upstream waveform changed slightly but was still up and down, and the post sensor changed to match the, whilst my top O2 sensor starts to go all over the place, and the post sensor follows it.
The garage said it was the CAT, but also said it might also be over fuelling, hence the erratic waveform but they were not sure.  Its uneconomic to repair so is now a hobby car, I'm going to strip it down, and make sure there are no air leaks, but won't be bothering until the summer of 2020.
I have a rough idea of what I am looking for to fix it, I'll let you know the result in 5-6 months time.
Thanks for all the help.

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 Posted: Tue Dec 10th, 2019 07:52 pm
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Paul S
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Mana: 
dont know answer to that, except your motor failed its MOT with a high CO% of 0.60 The output from the cat is around 100c lower than the input..so when you remove it your be able to view the honeycomb core & see if its intact..it all helps. thought you replaced the O2 sensor?. & on that one be sure its an OE equivalent sensor like bosch or ngk, some of the non oe aftermarket parts dont work to the same tolerances as the oe stuff.

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 Posted: Tue Dec 10th, 2019 05:02 pm
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Umpa
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Mana: 
Hi, well it arrived today and I did the test.  The output is around 100c lower than the input.  So I guess the cat is dead, so that's one half of the mystery solved.  I would like to know if the upstream cat waveform should remain a heartbeat throughout the rev range, or does it turn in to a rising trace during acceleration ?

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 Posted: Mon Dec 9th, 2019 04:38 pm
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Umpa
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Mana: 
I have the IR Thermometer on order, will report back when it arrives and have tested.

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 Posted: Sat Dec 7th, 2019 05:07 pm
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Stealth
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Umpa wrote:
Right, thanks chaps, I will have a look at that.  So anything under 300c means the cat is not working ?


300c is ballpark and can vary for a number of reasons.

As Paul suggested, with a hot engine, running at around 2500rpm, measure the temperature rise across the cat with an infra red thermometer. The outlet pipe should be higher than the inlet side if the cat is lighting up.

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 Posted: Sat Dec 7th, 2019 04:11 pm
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Umpa
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Mana: 
Right, thanks chaps, I will have a look at that.  So anything under 300c means the cat is not working ?

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 Posted: Sat Dec 7th, 2019 01:43 pm
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Paul S
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Mana: 
At 2500 rpm point the gun at the exhaust before the cat and then after the cat. The temperature after the cat should be higher indicating that its lit up.

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 Posted: Sat Dec 7th, 2019 12:22 pm
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Stealth
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Mana: 
Umpa wrote:
What do you mean by lighting up ?


The cat has to reach a working temperature, often around 300c, before the chemical reaction between exhaust gas & various metals in the honeycomb will convert/clean up the emissions.

Hence the term "lit up" when temperature is reached & the reaction starts.

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 Posted: Sat Dec 7th, 2019 10:39 am
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Umpa
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Paul S wrote: A CO% reading of 0.60 could be the cat an Infrared thermometer contactless temperature measurement gun, which dont cost to much, would indicate if the cat was lighting up.

waveform for O2 bank 1 trace was like a heartbeat, and bank 1 was flatline. dont add up.. Bank 1 is normally upstream, pre cat, Bank 2 is downstream = post cat.
What do you mean by lighting up ?

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 Posted: Wed Dec 4th, 2019 08:52 pm
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Umpa
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Mana: 
I might have got them the other way around, however when engine was at about 3000 rpm both waveforms were all over the place.
I don't want to fit a CAT if the problem is elsewhere.

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 Posted: Wed Dec 4th, 2019 08:15 pm
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Paul S
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Mana: 
A CO% reading of 0.60 could be the cat an Infrared thermometer contactless temperature measurement gun, which dont cost to much, would indicate if the cat was lighting up.

waveform for O2 bank 1 trace was like a heartbeat, and bank 1 was flatline. dont add up.. Bank 1 is normally upstream, pre cat, Bank 2 is downstream = post cat.

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 Posted: Wed Dec 4th, 2019 05:52 pm
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Umpa
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Mana: 
Would a screen video of the diagnostic help at all ?

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 Posted: Wed Dec 4th, 2019 10:59 am
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markt
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Mana: 
hi
if the rear lambda starts to switch at the same rate as the front one then yes it looks likely its a faulty cat,especially if the rest of youre readings are within spec.

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 Posted: Tue Dec 3rd, 2019 08:58 pm
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Umpa
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Mana: 
its a daewoo matiz.  What could  it be then do you think ?

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 Posted: Tue Dec 3rd, 2019 08:55 pm
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KevG
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Mana: 
It’s unlikely to be the Cat. What make and model is it ?

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 Posted: Tue Dec 3rd, 2019 08:43 pm
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Umpa
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Mana: 
Hi - we did that, what happens is that the waveform for O2 bank 1 trace was like a heartbeat, and and bank 1 was flatline.  Then as the revs increased both sensors started to go whacky.

So I am unsure if its a over fuel, air or anything other problem,  I'm guessing CAT due to its mileage.

Last edited on Tue Dec 3rd, 2019 08:50 pm by Umpa

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