General DECISIONS DECISIONS break or keep?
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General DECISIONS DECISIONS break or keep?
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I've only ever had a post cat sensor throw a EML for heater circuit short or circuit failure, not for performance.
What tends to happen is the post cats sensor readings tend to fluctuate depending on heat and drive cycle, which makes it difficult to reliably judge it's performance and set a finite level at which to flag a fault .
So what tends to happen is the ECU compares both sensors readings and if they are alike it knows the cats performance isn't right and starts warning the driver of an emissions fault rather than an engine fault.
Some vehicles have a dedicated emissions light, others don't and tend to flash rather than light the EML up solidly.
Try warming up the engine/cat fully and logging both O2 sensors.
The Pre should switch voltage about once every second, it's peaks and troughs should be around 0.9v and 0.1v and if fueling correctly it's average/mid point should be 0.45v.
Now test the Post sensor.
It's difficult to give an exact reading, as mentioned there are various things that influence the cat performance, heat and age being two, but it should smooth out the switching of the pre cats readings and return at slightly wobbly reading around 0.5v to 0.7v mark.
If it's not doing this, it's more than likely the cat isn't doing what it should.
The biggest issue with cats tends to be misfires that send upburnt fuel into the exhaust, this causes excess heat and starts melting the internals so it can no longer store the oxygen it needs to work correctly.
What tends to happen is the post cats sensor readings tend to fluctuate depending on heat and drive cycle, which makes it difficult to reliably judge it's performance and set a finite level at which to flag a fault .
So what tends to happen is the ECU compares both sensors readings and if they are alike it knows the cats performance isn't right and starts warning the driver of an emissions fault rather than an engine fault.
Some vehicles have a dedicated emissions light, others don't and tend to flash rather than light the EML up solidly.
Try warming up the engine/cat fully and logging both O2 sensors.
The Pre should switch voltage about once every second, it's peaks and troughs should be around 0.9v and 0.1v and if fueling correctly it's average/mid point should be 0.45v.
Now test the Post sensor.
It's difficult to give an exact reading, as mentioned there are various things that influence the cat performance, heat and age being two, but it should smooth out the switching of the pre cats readings and return at slightly wobbly reading around 0.5v to 0.7v mark.
If it's not doing this, it's more than likely the cat isn't doing what it should.
The biggest issue with cats tends to be misfires that send upburnt fuel into the exhaust, this causes excess heat and starts melting the internals so it can no longer store the oxygen it needs to work correctly.
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Whilst i can't help is the flashing absolutely regular or erratic? If regular it must be saying something?
Thank you for that explanation, it makes perfect sense. It sounds like it is the cat then. I guess for a 9 year old car with 136,000 miles it’s to be expected. I can pick up a cat on eBay for about £70 but do t think I can be bothered to change it in case that then leads on to something else and a particularly awkward job I imagine. I think my original reason for breaking it might be the way forward but who,r it’s got a couple of months MoT on it, I might drive it around for a bit.
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It's worth checking both O2 readings, I'm curious.
Another thing, has it been ran under load since you cleared the codes, or just idled?
It may have a misfire that's not apparent until driven.
I wonder if the cam and crank sensors are out of alignment and it's detecting a misfire?
If it is the cat, I don't think swapping it out is a difficult job, I don't think there's much in it's way, though I would want to be certain before forking out and tackling it.
Another thing, has it been ran under load since you cleared the codes, or just idled?
It may have a misfire that's not apparent until driven.
I wonder if the cam and crank sensors are out of alignment and it's detecting a misfire?
If it is the cat, I don't think swapping it out is a difficult job, I don't think there's much in it's way, though I would want to be certain before forking out and tackling it.
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Only ticking over. I’m going to take it for a spin over the weekend. Noticed today that there is a dent in the back of the roof and the hatch has a dent too. That’s made my mind up that I will break it up for spares.
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The warning light could be the alternator not charging properly. It will be interesting to see what you find when it's stripped out.
Just took the old girl out for a spin. When you unlock the door there’s a very loud electric motor that runs for about 6 seconds or so. Sounds like the fuel pump priming but really loud.
The old girl runs really well. Shame about that flashing engine light.
The old girl runs really well. Shame about that flashing engine light.
Bluetruck
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That would be the gearbox primer pump.
Bluetruck
New member
It primes the hydraulic gear change system on the gearbox. It is a noticeable noise, they all do that Sir?
More noisy than it should be?
[ame]https://youtu.be/J8LVy3NWAvg[/ame]
[ame]https://youtu.be/J8LVy3NWAvg[/ame]
Definitely doesn't sound healthy
Just as well I'm breaking it for parts then 
Eek yeah that sounds nasty. They're not quiet when new but it's more of a whir than that hissing sort of sound.
Given the performance of many Dualogics though, it's done ok to get to that mileage. Be interesting to know if it'd had prior repairs though, as they're not Fiat's finest effort.
Given the performance of many Dualogics though, it's done ok to get to that mileage. Be interesting to know if it'd had prior repairs though, as they're not Fiat's finest effort.
That’s what I was thinking. I’ve always avoided the autos and was amazed to see this one up for auction. It runs fine despite the noise.
car is well on the way to being dismantled. Apart from the tools all that rubbish was in the car. Some people are disgusting.Car went this morning, stripped to within an inch of its life. Picked up by IRC for a project car. 