disco 2 v8 emissions

hi guys.
took the disco back to the garage having fitted 2 new lamba sensors and new cat.
engine was hot.
co2 ok now , but still problems with lamba emissions high.
drove back and car was missing, got home checked under bonnet plug cap had come of one of the plugs ,so back again for another gas emissions test.
if its still not right what do i do next as getting to the end of idea,s.
any body done this problem before.
many thanks

Leaking exhaust is the usual for a high lambda reading.

hi checked the exhaust small pin hole in middle box.
also nipped up exhaust manifolds and inlet manifolds just make sure.
would this small hole make the differnce .

many thanks

only if its before sensors like manifold gaskets

jamesmartin said:

only if its before sensors like manifold gaskets

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Wrong,its even worse for a high lambda reading after the oxy sensors because after the sensor the engine ecu has no influence on what happens.Any air pulled in after the sensor will present a higher oxygen reading leading to the lean,(High) Lambda reading.

after the sensor only external tester will read added o2

hi just got back from the garage.
lamba reading was 1.238 should be 1.03.
dont know what going on with the engine.
new cat lamba sensors checked manifolds exaust etc.
now baffled.

many thanks

jamesmartin said:

after the sensor only external tester will read added o2

Click to expand...

Which is exactly the problem - it wont go through the mot.
With a reading that high I would be looking at a low Maf reading first.On live data look for 22-25 kg/hr at idle and more than 90kg at 3000rpm,engine hot all loads off.What were the Co and HC readings ?

hi the co reading was 0000 everything was ok except for lamba.
he said to much oxygen in the exhaust.
hoping to get it on textbook tommorw see what is happening.
could the maf sensor of packed up.

many thanks