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Author Topic: Faulty catalyst or lambda probe?  (Read 3480 times)

Offline gilesthedog

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Faulty catalyst or lambda probe?
« on: June 07, 2015, 09:19:06 am »
Hi there, just had the standard downpipe replaced with a 3" stainless with sports cat from jap parts eBay shop. All seemed fine on first long run of 200 miles but 2 days later on a short trip the exhaust warning light has come fully on, manual says this indicates exhaust gas problem. Anyone got some idea if this could be a faulty catalyst or lambda, or do I need a remap to sort out fuelling?
Also,if I ignore for a few weeks is there a risk of damaging the catalyst from incorrect fuelling?
Cheers, Tom

Offline AJP

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Re: Faulty catalyst or lambda probe?
« Reply #1 on: June 07, 2015, 09:15:36 pm »
It's normal for that to happen when you uprate the downpipe/cat, so don't panic.

A competent mapper can sort this. And if you're not already remapped it's the perfect excuse to turn up the ponies :-)

Offline gilesthedog

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Re: Faulty catalyst or lambda probe?
« Reply #2 on: June 08, 2015, 04:39:47 pm »
Thanks for the re-assurance, my mechanic seems to think it'll be safe to drive until I get the mapping done, now that it has an Evoms intake with the downpipe it's ready for some tinkering, just waiting for pay-day to fund the ECU map, DSG map and fuel pump check.

Offline gilesthedog

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Re: Faulty catalyst or lambda probe?
« Reply #3 on: July 22, 2015, 09:45:21 am »
Just had the engine and DSG re-mapped so the warning light was reset, a day later it came back on and the garage say it's the second lambda probe registering a problem. Their suspicion is that the sports cat is not efficient enough to clean the gases to the required levels and hence the error, talked to Japparts ( Jap Parts, 120 Bark Street, Bolton, UK, Lancashire, BL1 2AX ) who supplied the downpipe and they say it's not something they're aware of and can replace the pipe within the 6 month warranty they give. Seemingly the second probe can be disabled so it doesn't actually provide readings to the management system, but not been told if this will cause more issues and whether the car will fail the MoT in a months' time.
Dilemna now is whether to wait for the MoT and see if it fails, then get it replaced under warranty and cross fingers the new one does the job, or to cut my losses and stump up for a full Milltek or BCS system.
I've seen others in the forum fitting these cheap downpipes and didn't notice anyone having similar issues, any guidance or advice on how to proceed ?
Thanks,  Tom.

Offline Powervalve Nige

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Re: Faulty catalyst or lambda probe?
« Reply #4 on: July 22, 2015, 01:05:39 pm »
Hey Tom
The tolleranaces set at the factory are quite tight regarding the post cat sensor - basically the ecu is reporting back saying the VAG cat has developed a fault, when in reality it's not there it's been swapped out. So first thing to do is recongnise that as already stated this is always going to happen... Most stage 2 remaps remove this line of code and therefore eliminate the CEL.
However, the most important consideration is its fitness for purpose in terms of its road legality. Generally the cats on EBAY are 4.0" dia with a limited precious metal wash coat (as low as 5 grms). Not necessarily an MOT fail - but entropy dictates that over time the wash coat will erode, and thats why cat manufacturers limit the warranty they offer.
Always ask the question before purchasing what the pm content is - if they don't know or are reluctant to give up the info then be warned...
The first thing you need to do is take your car down to the local friendly garage and ask for a pre MOT check on your exhaust gas - this involves a 10 minute check with the probe up your pipe (the car...) and an analysis done to show the readings relative to current legal requirements.
If its struggling now then you need to bear in mind how it will be in the future and get a refund stating the readings and its fitness for purpose.
Hope this helps
Nige
happy to talk to you about our fully road legal oversized cats...


Offline Jay75

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Re: Faulty catalyst or lambda probe?
« Reply #5 on: July 24, 2015, 04:22:23 pm »
I had the exhaust fault come on too when I had my down pipe fitted, it went out after a while and then just popped up now and again after that. It passed 2 mot's like that and was never a problem, Quick-fit mot's too!!

Offline gilesthedog

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Re: Faulty catalyst or lambda probe?
« Reply #6 on: August 20, 2015, 09:05:06 am »
The mapper disabled the second lambda and reset the fault, it's been a few weeks and no issues, just passed MoT with no emission issues at all, happy days.
Tom

Offline patpong_pete

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Re: Faulty catalyst or lambda probe?
« Reply #7 on: October 05, 2015, 01:22:39 pm »
Hi guys
went for a drive yesterday and all fine then on way home
exhaust warning light has come fully on,
manual says this indicates exhaust gas problem.
Anyone got some idea if this could be a faulty catalyst or lambda,

its on standard exhaust please advice and help
thanks in advance for reply

Offline patpong_pete

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Re: Faulty catalyst or lambda probe?
« Reply #8 on: October 05, 2015, 06:13:38 pm »
Hi guys
went for a drive yesterday and all fine then on way home
exhaust warning light has come fully on,
manual says this indicates exhaust gas problem.
Anyone got some idea if this could be a faulty catalyst or lambda,

its on standard exhaust please advice and help
thanks in advance for reply

what are your thoughts guys

should i get on vag com to see fault or reset ?