E46 M3 Failed MOT - Emissions Problems...

[tbmeech]

Chaps,

My car failed it's MOT yesterday, my emissions were through the roof, the rest of the car was absolutely fine.

Has anyone had their M3 fail an MOT due to emissions problems? if so, what was the cause?

Car is pretty much standard (engine wise) bar ITG filter, Supersprint Centre Section and a Dixis back box.

Was quite suprised it failed, though last year the same guy had trouble with the emissions, but put it down to the 100 cell cats I was running at the time.

It's going back in tomorrow for diagnostic etc, but I'm a bit worried as he's not a BMW® specialist, just my local garage and I don't think he knows too much about M3's to diagnose the problem...

It's due an Inspection 1 service in 3-4 weeks, I could get it serviced early, but would rather not if I can help it as i'm doing myself out of money by doing that with the mega miles i'm now doing.

[XKaLiBaR]

have you got the standard cats on the car now?

Mine passed fine, with the miltek 100 cell cats, non reso xpipe, and the supersprint lightweight exhaust.

[Davidch]

It probally failed due to the fact it's a shed!!! :D

From memory my old CB M3 had high emissions, but passed I had the Larini Back Box.

Have you thought about trying a free MOT test centre, if you fail then no fee?

[westside]

have u taken th ecar on a long journey or do u drive around town, if you havent given it a long burst id stick some cat cleaner in and give it a run. Or it could be a lamda sensor but that would normally through up the EML light.....

[mikem]

Have you thought about trying a free MOT test centre, if you fail then no fee?

I thought they all worked like that ? No pass, No £20 for a drink. :D

[k31ths]

Mine failed yesterday for a suspesion arm and the ball joint having exessive wear. Its the second time its gone in two years, which pissed me off.

[Doc Matt]

Give it some long distance rapeage right before the test. S'mazing how much it lowers it.

[mnathan]

Give it some long distance rapeage right before the test. S'mazing how much it lowers it

Yup.......the hotter the cats the lower the emissions.

[sjj84]

Yup.......the hotter the cats the lower the emissions.

How does this work then out of interest? I've heard it mentioned quite a few times but never known why a thrashing works.

[mnathan]

How does this work then out of interest? I've heard it mentioned quite a few times but never known why a thrashing works.

As far as i understand it , by heating the precious metals in the cats, it promotes better reactivity , thereby binding more efficiently with C02 and lowering the resultant quantity in exhaust fumes.

[tbmeech]

have you got the standard cats on the car now?


Yeah Baris, back on std cats for now, might get some Supersprint ones soon though...


It probally failed due to the fact it's a shed!!! :D

Mutha Fucka!!! :D

Car had a decent blast before I got there, was still high, had been out for a good hour before the test was conducted, so not sure, had similar probs last year, but he fudged it thru.

Wondering if its the lambda sensors or something...

[tbmeech]

All sorted now, was indeed the lambda sensor pre-cat on bank1, the connector block had some corrosion on the contacts so the lambda wasn't heating up like it should, the guy cleaned it up and hey presto, normal emissions readings :)

[XKaLiBaR]

nice one. good to know for when mine gets buggered :D

[tbmeech]

Exactly, I thought it might be Lambda's in the first place, they did say they need changing in about 10k miles or so, I might just order some new ones up as they are only £70 each from ECP anyway...