disco 1 3.9v8 1994 with cats white tune resistor. right here we go engine at normal operating temperture. sitting at idle 1st emission test result 0.6 to 0.9 then 2nd test at 2000rpm 1.3 -1.5 .is this good.this is with my own gunstons c02 gastester. going to garage tomox just to confirm.

Those numbers look like a fail. Max CO% at idle should be 0.5% and the fast idle test should be 0.3%. Max lambda 1.09, min lambda 0.95 all tests should be with a min. oil temp of 70 Deg. C

The idle figures are close but I would have a bit of a worry on for the fast idle, that's way high, are you sure the O2 sensors are switching?

hi kev when i put ecu m8 both lambas are running lamba 2 does try and flick to lean. also could it be my cats because i have old after market ones on there and whats strange is if i start the motor without middle box on its really noisey raspy. but my son in law has landrover cats fitted on his and if he starts his motor without middle box connected its no way as loud as mine more of a deep sound. so could my cats be letting more co2 gases pass which gives a high reading still. also i have got some secondhand original landrover lambas as mine were after market ones. what would you suggest.im at my teather with this now.

Aftermarket cats are notorious for not lasting long so if you can change them it will probably sort it. Your gunson tester probably won't be sensitive enough.

Mick

cheers mick