Failed MOT Emissions

fo0k · Post by **fo0k** » Mon Apr 22, 2013 1:21 pm

98' F
HGF replaced about a year ago - is still solid.

Last MOT passed with no emissions problems. this time its reading 5.0 (I think 0.3 is a pass? so this thing is a long way off.)

the Lambda sensor 'fell out' a few weeks after the successful HG replacement and MOT... and was replaced/welded back in by the garage.

now, a year on the emissions are all over the place and Im thinking that fuel consumption will have also been increased as a result.

How can it get so high in one year? Can a screwed up job of this lambda be the sole cause?
Also, would the lambda sensor have been removed during the HG replacement?

Any thoughts appreciated, thanks guys.

Post by **colintf** » Mon Apr 22, 2013 3:03 pm

What cat do you have and how old is it??

andywatson · Post by **andywatson** » Mon Apr 22, 2013 3:38 pm

If the lambda hasn't been fitted correctly or is faulty this would cause damage to your cat and result in high emissions.

fo0k · Post by **fo0k** » Mon Apr 22, 2013 3:52 pm

I couldn't say too much about the CAT Im afraid but for sure 'old and knackered' is probably fair. (car is in the garage currently so unable to check)

but I get the impression that even without a CAT these readings are far too high?

thanks!

Martin_Bmth · Post by **Martin_Bmth** » Mon Apr 22, 2013 9:26 pm

Hi,
Ive got similar but not quite so catastrophic symptoms.
Im pretty much a newbie but its nice to share these things and most of the advice is from this forum

. Ive changed the cat and its about the same and just to rule out burnt out valves ive done a compression test and that seems ok.

Ive currently got a new lambda and brown sensor on order from the bay, should be here in a day or two. The "theory" im going with is that the brown sensor fails/ gets lazy and the car overfuels as it thinks its always cold, damages the lambda and washes out the cat (in your case id suspect the lambdas suffered during its escape attempt). Like the holy trinity of emissions, one goes belly up, they all go belly up. I could be wrong

Oddly enough all the problems with high emission seem to display symptoms of poor idling/ hesitancy at some point, but my car appears to runs pretty sweet when its hot or cold. Does yours idle ok?

After that there is a theory that there could be an injector being clogged and just dumping fuel into a cylinder (but plug condition doesn't show a specific cylinder being extra sooty) or the fuel pumps running at the wrong pressure. Another theory is my cars got a scorpion exhaust that maybe not giving enough back pressure causing a bad air/fuel mix. Lots of threads point you towards going for genuine parts and putting everything back to standard!

Ive gone for 'bay bits, they're too cheap to resist but ive also gone for the ones with as near 100% positive as possible and thousands of feedbacks so Im fairly confident the bits aren't duff.

Will let you know how the new sensors react.

Depending on what works I might have a spare sensor/ cat that's still good to swop around for you

fo0k · Post by **fo0k** » Tue Apr 23, 2013 3:49 pm

right well all interesting. currently garage saying computer appears to be causing the fault.

not sure if I should be dubious or not on that one. computers tend to be either 'correct' or do nothing at all in my experience. they don't usually start making different decisions.

idling does seem to be ok. going to pop down there now and see what the deal is and will report back.

fo0k · Post by **fo0k** » Fri Apr 26, 2013 2:13 pm

All checks have been made on the vehicle and I'm advised the ECU is faulty and causing the issue.
does this sound reasonable? Spoke to An MGF specialist who cannot remember ever replacing an ECU on a 98'F for emissions.
Getting a bit disillusioned with it all now.

All I know for certain is that after the HG replacement, a month later the Lambda sensor was hanging off the bottom of the car as stated in my first post.

Can someone confirm whether the Lambda sensor would be removed during a HG replacement? - For certain / probably / probably not ?

(the CAT may well be an additional factor here but I would like to try and eliminate what I can ..tricky on a forum but best guesses are welcomed)

thanks guys.

Reckless Rat · Post by **Reckless Rat** » Fri Apr 26, 2013 3:16 pm

Well, if we're talking about the exhaust manifold lambda sensor, it's likely that it may have been disturbed during HG work as the manifold has to be removed. Take with a pinch of salt what your garage is saying as I agree that it's very unlikely that the ECU is at fault (I hope so anyway!). Most emission problems are lambda related or, as already mentioned the exhaust cat. The fact that your garage had to weld the manifold suggests that they've probably bolloxed something, probably stripped a thread. The lambda probes are prone to seizure but can normally be removed on the bench with a bit of help. Best way to check is to remove the engine access panel and then grovel round to remove the exhaust manifold heat shield. You'll find the lambda on the "inside" of the top section of the manifold. There's also a connector to the loom mounted on the n/s of the engine near the coolant rail.

One final thing. If the lambda joint has been leaking, or the exhaust flange/head or lower flange then your cat may well be buggered. However I would change the lambda & take it from there.

yogi63 · Post by **yogi63** » Wed May 01, 2013 7:53 pm

Hi, . I'm new to this. Just had my MGF fail miserably on its MOT for emissions. They were off the scale

Not sure now whether to get rid or try and repair, few other bits need changing too. What to do? Any sensible suggestions please.

robda · Post by **robda** » Mon May 13, 2013 1:39 pm

think my readings on last mot were 6.sumink they changed the lamber sensor 90+ quid still 6.sumink recconed it could have been the ecu or crap fuel went on ebay fitted new cat took me about hour n passed with .1 so best bet change the cat there not that pricy you will prob need to change the steel band round your back box aswell

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