R400 Duratec MOT emmisions fail

[Andy Green]

So MOT yesterday. Failed only on emissions.

 

Thought it would the RBTC needs to be balanced again.

 

So checked balance and are spot on. Spark plugs all look good.

 

No other running issues.

 

Failed everything i.e. High CO, High HC and low Lambda

 

CO was over 7% Should be < 0.2

HC over 1000 ppm Should be <200

Lambda 0.73 Should be 1 +- 0.03

 

We has a play for a while on this. As we went up the rev range we could get HC or CO in range but never together. Lambda seemed to be very low or very high and never seemed to be in range.

 

So just the local MOT centre not at a Caterham garage.

 

So plan is new spark plugs as I have a spare set and try a new Lambda sensor.

 

Any other suggestions?

 

 

[Slipper man]

Find a garage that is more used to/ friendly about Caterhams. Having said that, the readings do look rather odd and I wonder whether it might be in your interests to get the mapping sorted out by Steve Greenauld. You will probably find that not only will the car pass its MOT, but it will drive better too.

[jimh]

I had my CSR remapped by the two Steve's last year and this year I had trouble getting it through the emissions bit of the MOT.

Mine was failing on the lambda but after some fiddling about we got it to pass. I'm hoping to find the time to get Steve to check it over and see if there is anything wrong with the map.

[Andy Green]

Thanks for the comments.

 

I should also have said that the car has not been upgraded or changed since the last two MOTs when it eventually passed both times well within the limits. I did have to balance the Roller Barrel Throttle Bodies. So the map might not be perfect but can certainly get through an MOT.

 

I am trying really to understand the most likely thing that has failed. My guess is the Lambda sensor.

[6speedmanual]

My winter blatting car failed MoT emission with almost identical set of readings to yours Andy Green.

They indicate the cat is doing little or nothing. Even if the closed loop has failed the cat should be promoting oxidation of the CO. Also running so rich suggests the closed loop is really not working.

If heard comments that prolonged rich running (potentially from dead lambda sensor) can "wash" cats of their active coatings.

Solution: new cat and lambda sensor and all was tickety boo.

 

Peter

[Andy Green]

I invested in the Easimap 6 cable and downloaded the software onto an old laptop and confirmed that the ECU never controlled to Lambda. i.e. I could never get a stable 1.00 reading. It was always changing from max to min.

 

So invested in a new Lambda sensor. Result I think. The ECU will now controls to Lambda i.e. 0.99 to 1.01 fluctuating reading once the engine has reached 100C according to the ECU. The car gauge reading just over 80 as normal. As soon as the temp drop to 95 is drops out of Lambda control.

 

Off to MOT station......

 

Initially the HC and CO are OK but Lambda is out which is what the ECU is saying.

 

We have another go with it controlling on Lambda and we get the HC is OK but the Lambda is reading low i.e. 0.95 ish and the CO is up to 3%

 

How can the engine control to a Lambda of 1 but after the cat it is 0.95?

 

Are these symptoms of arriving with a hot cat and it working initially and then cooling down?

 

Is this a case of I need a new Cat or do I need to find a 7 MOT station that will play around and wait to get a set of reading that work?

 

Car has only done 8500 miles.

 

Should I get a new cat and a bypass pipe and just fit the cat for the MOT? Seems a lot of effort! Even with a defective Lambda sensor would you expect it to kill a cat in 4000 miles which is all I gave done this year.

 

Interested in any thoughts before I make further investments !