S1 emissions failure

[Callet]

My S1 111s (5 years old) has failed its MOT due to emissions. Even a new CAT won't bring it down to the requirements. Anyone have any idea what might be causing this. . .

>> Edited by Callet on Sunday 23 October 20:53

>> Edited by Callet on Sunday 23 October 20:54

[trackcar]

sounds to me like the cause is a bad diagnosis by your garage, hope they haven't charged you for the cat .. go somewhere else that knows what they're doing maybe? a scan of the emmissions print out might help though

[ChristianM]

Was speaking to miles at fibreglass services about this on wednesday. Apparently the reduced back pressure of some aftermarket exhaust systems can cause this problem on the S1. I don't know if you have such an item fitted however...

[johnnyhayward]

trackcar said:

sounds to me like the cause is a bad diagnosis by your garage, hope they haven't charged you for the cat .. go somewhere else that knows what they're doing maybe? a scan of the emmissions print out might help though

I don't think the garage being wrong is the only answer, have you checked things like the lambda sensor ?

If you can tell us the readings you've been given some wisely chaps on hear should be able to help you better.

[trackcar]

lol. erm well it sounded like the diagnosis was a faulty cat, and a new cat didn't cure it. Generally emissions problems aren't down to the cat at all, but more likely as you say to be a sensor problem which may then go on to damage the cat if not corrected early enough. we really need that failure data sheet.

[Callet]

Thanks for your thoughts. I shall try to get some more info on this

[stone]

trackcar said:

lol. erm well it sounded like the diagnosis was a faulty cat, and a new cat didn't cure it. Generally emissions problems aren't down to the cat at all, but more likely as you say to be a sensor problem which may then go on to damage the cat if not corrected early enough. we really need that failure data sheet.

Far too many places will instantly change the cat due to emmissions failures. A cat cannot fail on it's own. You have to find the cause of failure before replacing or you'll just shag up the new cat

[scuffham]

agree with what has been said, except, the silencer has NO EFFECT whatsoever on the emmissions (assuming it does not have a hole in it!)

first thing to check BEFORE changing things is what is the Lambda reading on the test?

if it's NOT 1 (+-0.3) then forget the rest, fix the problem, this will either be the lambda sensor or a hole in the exhaust ahead of the sensor and/or tailpipe.

[nick1181]

the same has just happened to me with my 2000 S1 elise, the cause of the problem was the exhaust its self not the cat. The standard exhaust has rotted and there was not much comming out the tail pipes most of it was comming out of the box and into the bodywork. This seroiusly effected the emissions that came out and it failed.

I have changed the exhaust to a Christopher Neil sports exhaust and it passed with flying colours!!!

Check the actual exhaust.

[Callet]

Thanks Nick - I have a Janspeed exhaust but will get it checked.

[dss123]

Si,

Like the guys have said - start by looking at the failure sheet - which reading was too high?

If it is the Lambda reading (mine was last year) then it is probably a sensor or, as others have said, a hole in the system sending the sensor loopy.

Check all connections first because the Lambda sensor ain't cheap! (£50 - £70)

If all stacks up. Make sure you give your motor a damn good thrashing to get the CAT red hot. TheN ask the MOT station to check the emissions straight away.

Best of luck


Dunc

[Callet]

Thanks Dunc - will try that - should get the data tomorrow too, so hopefully this will shed some light.

Thanks also to everyone who has posted on this - much appreciated.

[marsh]

Same happened to mine. Answer was to get it warmed up and passed fine. Sounds like it is not that uncommon according to B&C

[Callet]

I am told it was the Lamda sensor. Unfortunately this has ruined the CAT - but at least I now know.

Time to raid the piggy bank once more. . .

[DSS123]

Si,

Sorry to hear that mate.

Now, did the garage fit a new CAT in the first instance??

If they've buggered that before checking the Lambda sensor then it's their fault and I would kick off.

I'm not sure how bad things have to be before the CAT can be damaged by a faulty Lambda sensor anyway. It depends if the engine has been running rich or lean as a consequence. I would be asking the garage some searching questions!

If it does all need replacing, you can normally pic up second hand CATs on ebay or seloc for around £50. But like I say - the sensor is pricey and you want to get a new one. Fitting is a nightmare on an S1 - you can do it yourself but be prepared for a good few hours work.

cheers mate


Dunc

[Callet]

No, it's not the garage Dunc. I bought the car about a year ago & this was the first MOT. The garage looked into the emissions failure and diagnosed the Lamda sensor as faulty. Unfortunately the CAT was already as good as dead. They have sourced a CAT for me now at a pretty good price, but thanks for your advice.
I wonder if the previous owner knew about this when he sold it to me. . .