Mot fail Lamda
Discussion
Hi all. First mot for my mk1 tuscan and its failed on lamda. Pass figure on his analysier shows as 1.030 and best we could get was 1.125. Anyone have any ideas on what to do.
I have no idea if the cats have cat in them. I will look at this when it cools down.
Any thoughts appreciated.
I have no idea if the cats have cat in them. I will look at this when it cools down.
Any thoughts appreciated.
The cat won't affect the lamda readings. CO yes, lamda readings no. Probably a blowing exhaust. Start by looking for exhaust leaks.
Did the MOT tester try and diagnose the fault? If you unplug the lamda sensor and the emissions reading on the MOT analyser don't alter, then the lamda sensor is faulty.
Was the probe sufficiently far into the exhaust?
Did the MOT tester try and diagnose the fault? If you unplug the lamda sensor and the emissions reading on the MOT analyser don't alter, then the lamda sensor is faulty.
Was the probe sufficiently far into the exhaust?
The place around the corner that I have started taking my Tuscan to had trouble with the emissions test last year and this year. They where scratching their heads as the owner said he could tell it was fine (apparently worked on a Tuscan racer in his youth) but could not get a good reading. I had read before on this forum that the speed 6 can be difficult if you don't know what your doing and a quick google to jog my memory sorted the problem! Stuff some wadding/ rag around the probe to block up the can opening and all was well. Not sure exactly why but the reckoning was the exhaust has quite a bit of suck back between strokes (stick your hand over it to see) this combined with the diameter of the can and the depth of the probe into the can possibly screws with the reading as it sucks too much air back into the pipe. This could all be rubbish I'm spouting but the rag up the pipe solved the issue last year and this year. His machine did alter its test to a much longer one I seem to remember. The rag started to get a bit toasty! No idea if this was your problem but it may help. Apparently the focus ST suffers from a similar issue.
This is why the breakdown of gasses is so necessary... many a car fails on the 'lambda' value because of a small airleak upstream in the exhaust system causing the oxygen content at the tailpipe to be too high... nothing to do with the combustion products, nor the efficiency of the CAT, just that the tailpipe sample is 'too clean' as it's being diluted by drawn in air... oh the irony!
The effect on a car with lots of valve overlap is the same although the cause is different, as outlined in the previous post, preventing air being drawn back up the tailpipe and into the probe proves that.
But we don't yet know what the OP's breakdown of gasses is....
The effect on a car with lots of valve overlap is the same although the cause is different, as outlined in the previous post, preventing air being drawn back up the tailpipe and into the probe proves that.
But we don't yet know what the OP's breakdown of gasses is....
I have spoken to the mot station and the guy is happy to look at the document and it should pass based on the new figures.
Additionally today i have done a balance of the itb’s and reset the adaptive maps. What a different car. For now anyway.
Lets see what next week brings when i go for the retest
Additionally today i have done a balance of the itb’s and reset the adaptive maps. What a different car. For now anyway.
Lets see what next week brings when i go for the retest
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