M.O.T failure on Emissions

[excalibur1814]

Hello,

Just back from an mot test and... it failed. 2004 Roadster with the TTE exhaust, new MAF around 8 months ago, with new filter, but that's about it.

Emissions:
Fast idle test
Min Li Max Li Actual
RPM: 2350 - 2650
CO - 0.300 - 0.125 Pass
HC - 200 - 155 Pass
Lambda 0.970 - 1.030 - 3.496 Fail

2nd Fast idle test
Min Li Max Li Actual
RPM: 2350 - 2650
CO - 0.300 - 0.128 Pass
HC - 200 - 164 Pass
Lambda 0.970 - 1.030 - 3.273 Fail

The results above are from the left side of the exhaust exit with the other side, of the exhaust exit, being a fail on all three. Going to see if there's any error codes after work (No actual warning lights on the dash).

So... Exhaust, sparks, clean maf? The guy testing seeming mightily confused with how the exhaust was acting.

Thanks all.

[SonicSW20]

I'm not surprised the tester was scratching his head. Are you sure it was reading a lambda value of over 3? That would mean the gas analyser was reading mostly fresh air. A lambda value of 1.000 means 14.7:1 AFR. Going up to 1.100 means an AFR of 16.2:1.

Are you sure your exhaust is even connected to the engine?

[mr2garageswindon]

I'd be getting it tested on another gas machine to be sure... I've never seen results like that.

[excalibur1814]

I've checked the figures and added dashes just in case. A guy, here at work, has a code reader so hopefully he'll appear and check. (He owns a crazy Mk2 import).

[SonicSW20]

If you're genuinely getting 3.2 - 3.5 lambda at the tail pipe then there must be a lot of air getting into the exhaust stream. There's simply no way the engine is actually running that lean.

[excalibur1814]

No errors on the reader at all.

It'll be going up on a lift after 5 and we'll have a good damn look.

Will update asap.

[SonicSW20]

If the leak is downstream of the o2 sensors then the ECU won't know anything is wrong, which would explain why the lambda reading is so high yet the car is working and not throwing any codes.

[excalibur1814]

Took it to another garage that owed me a favour and:

It passed.

Easily.

Took the car back to the garage for a re-test (Different guy) and it easily passed again. Only difference being that they both stuck the sensor in the right side and blocked the left.


Also disputed the front brakes failing on the left side so the guy tested them again and they also passed with ease.

Yay to a happy ending.



Thanks all!

[SonicSW20]

Strange! At least it was a simple fix