my mams rover 820, on a n-plate, just failed her m.o.t...


''rear exhaust box has a major leak of exhaust gasses''

''emmisions co content high at idle''


'' '' '' '' after 2nd idle excessive''

lamda reading after 2nd fast idle outside specified value.


3.56% co at natural idle (should be under 0.5%)

2nd fast idle co 4.807% (should be under 0.3%)



what could cause this? the exhaust(though i doubt it)?

 

Put a back box on it
Your getting an intake of oxygen hence why it has failed

 

I didn't think they would even test the emissions if there was a leak somewhere....

 

ok, thanks

 

In most cases thats correct not sure why they have this time ?

 

most stations do if car has failed on anything else, as if theyd failed it on say a broken spring and exhaust blowing and youve fixed both but then on retest fails emisions you could argue that it never failed emissions first time round, so they test emissions and say its failed but "could" be due to blow in exhaust etc.

hth

Tricky

 

very unlikely that a leak that far back in the exhaust and that far away from the lambda sensor would cause the rich readings.
It "could" be a faulty lambda sensor, but also have a good check round the pipework that connects the MAP sensor (which is in the ECU, pipe comes off the ECU) to the inlet manifold. A small leak here can make the MAP sensor read a higher pressure than is actually there and overfuel.

 

like rich says
an exhaust blow will cause the lambda to be high
however it would also drop the co, not raise it
so you have some other fault as well
regardless of the cause,if you have used it a lot the catalytic converter is probably now destroyed by the fuel so will probably need replacing once you have repaired the fault
rovers are the worst engines for this type of thing unfortunately