This car is failing emissions test. High idle CO @ 0.6 Low idle CO @ 0.7 Lambda @ 0.98. Car was referred to me from another garage. New OE 5wire pre-cat lambda fitted new OE post cat lambda fitted new cat fitted. No faults stored. Brain Bee wont allow me to see live readings for lambda switching voltage. I had a similar problem on a Golf 02 with bosch system and went through the usual and got it cured with cleaning up ecu earth to body and contact cleaner on ecu terminals. Tried this on the Seat but no difference. Occasionally, emissions will be perfect, ie, 0.00CO Lambda 1.00 but not consisstant enough. Any ideas out there?

Hi Morgan,

What voltage do you have on the post cat sensor when the fault is present ?

Regards Glyn

Is this one of the engines with a pcv on top? had a couple of them fail, causing bad emissions for mot.

With engine hot, fan cutting in, at high idle, lambda @ .975 co @ 0.96 the signal wire on d after cat lambda goes slowly from 0.81 to 0.88 volts.

There is a small one way valve on the cam cover close to the cam sensor and then there is the crankcase breather box which has one maybe two harnesses connected to it.

Hi,Morgan,
Just had problem with an Altezza with similar readings.No fault codes.Got injectors cleaned and readings stabilized.

Also had to replace cat.as it got damaged by over fueling or age.Might be worth checking for smoke on high idle test.Was cat an oe part.
Regards Christy

Morgan

You need to get live data to move forward on this, Have you tried EOBD ? you should get lambda & fuel trims which should at least give an indication of what the ECU is thinking.

remember this will be a wide band sensor so wont switch as traditional sensor does.

cheers Aidan