7 replies to this topic

[d4v1dtyler]

My mini cooper MPI failed its MOT on emissions.

These were the results:

FAST IDLE TEST


CO %vol:

Max:0.300 Actual:0.005 = PASS


HC ppm vol:

Max:200 Actual:36 = PASS


LAMBDA:

Min: 0.970 Max: 1.030 Actual: 1.132 = FAIL


Does anyone know what would cause this?

[Bungle]

is your mini standard or modified ?

[d4v1dtyler]

is your mini standard or modified ?

sw5 cam, and stage 3 cylinder head. Standard manifold with the backbox with pipes exiting from both sides.

[Silicon Skum]

That reading means that there is too much O2 (oxygen) in the exhaust gasses - Lambda sensor may be faulty, the mixture may be too weak or there could be a hole in the exhaust system. Could also be that you are using a fuel that has ethanol in it, it can throw the readings off. The other things are more likely though.

I think there is one other cause, but not sure what it is off hand.

SS

[minivanman]

have you got an LCB manifold? and if so is the lambda sensor in the Y piece or one of the branches?

[Sprocket]

CO is a little low.

It could be Lambda sensor, but if that checks out and is working fine, its a leaky exhaust

[d4v1dtyler]

Sprocket, would the leak need to be after the lambda sensor to get these sorts of results? Just i have just taken the top of the manifold off and on the join (connecting top of manifold to the down pipe bit) the mating surfaces were quite filthy and could have well cause a leak. Could this be the culprit?

[Sprocket]

You need to check to see if the lambda sensor is working correctly first.

A leaky exhaust can either be before the lambda sensor or after, the leak will draw air into the exhaust, and the MOT station gas analiser will pick it up as high lambda. If the leak is before the lambda sensor, the CO will be high and the Lambda high. If the leak is after the lambda sensor, the lambda will he high but CO low

Like I said, if the lambda sensor is working, its a leaky exhaust.

Its not missfiring as the HCs are low.

You really need to check the lambda sensor is working correctly, if it is found to be stuck low, test its operation. Dont think that because the lambda sensor voltage is stuck low, that the sensor is faulty, other things can casue this, such as a faulty lambda sensor relay.