I have a honda civic 1993 lsi with high CO emissions level reading at 2.70% and lambda levels are low.please can you give me any advice on correcting these levels for it to pass its MOT. Thanks

CO? That means Carbon Monoxide - it's a rather toxic and poisonous gas emitted from the exhaust system.

When they check emissions on cars CO is one of the gases they measure. If the level is too high .. your car fails the emissions test. I believe in the USA the emissions test is known as the 'smog test'?

If you have a problem with excess CO emissions on a car the cause is often an incorrect fuel/air mixture or a faulty sensor called the lambda/oxygen sensor in the exhaust system

on CO cars, it's below the ECU/PCM
but if you have lambda's, then its not a CO car.
CO cars are missing 02 sensors.
and you said, Sensors, as Plural. got 2?
you failed to post where car is and where it was sold new.
Or VIN.
Engine controls vary by country.
this car may be OEBD type ECU/PCM , "use a scan tool"
and if motor is rich , that can be for 2 reasons.
ENGine is rich
Catalysis dead, or both.
and CO is not HC.
but high CO usually does, give you high CO.

Emission test by codes reader? or smog? Any codes?

Replace your oxygen sensors.
murf427

We're these at idle readings ? What were the off idle and cruise readings, if available ?

evacuate system and refill to proper spec for r13a refridgent may not have proper levels. check cooling fan opperation with engine running cooling fan should be opperating while a/c compressor is engaged. if all theese check out good has blockage in system

Change the lambda/oxygen sensor in the exhaust.

Check vvt servo motor

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.

clockwise is down and counter is up

check oil level with engine running ,handbrake on and chock the drive wheels ,then drop into reverse and then check oil level DO NOT REV ENGINE WHILST DOING THIS