My mates mr2 rev3 failed his MOT today on emissions.

Tester said it was reading about 6-7%CO.

We checked the diagnostics port with bridging TE1 and E1 to see if this revealed any error codes and got nothing.

Can anyone suggest what it might be as all i can think of is the lambda sensor

(which should have come up id assume).

Fuel consumption is very bad too, if that means anything