MOT Emissions (CO)

[Splat90]

Make: Ford
Model: Fiesta Zetec
Engine size/Type: 1.4
Year: 2004
Mileage: 86K

OK so MOT failed due to CO emissions during natural idle but appeared to be fine during fast idle. Any help appreciated at this time need to get back on the road ASAP and cannot figure out what could cause this. Everything I have seen online shows CO fail at both natural and fast idle speeds.

Measurements

Engine Oil Temp --- Min 60 Deg C --- Actual Value 60 Deg C --- OK

Fast Idle Test
Engine Speed --- 2500-3000rpm --- Manual Check --- PASS
CO --- <=0.200% --- 0.101% --- PASS
HC --- <=0.200% --- 75ppm --- PASS
Lambda --- 0.970-1.030 --- 0,998 --- PASS

Natural Idle Test
Engine Speed --- 450-1500rpm --- Manual Check --- PASS
CO --- <=0.300% --- 0.807% --- FAIL



If it was my cat would I fail at both fast and natural?

I will admit my pre cat lambda sensor was broken for a good few month leading up to the test and I only replaced it 5 minutes before the test, could this be the cause and it needs "running in"?

Could burning oil cause this?

Could I possible fix this by removing my air filter for the retest so there is no restrictions, reducing possible leakage?



Any and all ideas welcome.

 

[andyandy2]

Air flow meter or MAF sensor

 

[Burnerman]

I'd go for a can of Forte fuel treatment and then get the cat bloody hot before the re-test......the engine seems cool to me at 65 degree oil temp, 90 is more usual.
John

 

[Belle427]

Id agree with getting it nice and hot ie an "italian tune up"!
Did the defective lambda sensor flag the management light at all?
It may need a few miles under its belt for the ecu to learn the new sensor.

 

[Splat90]

Id agree with getting it nice and hot ie an "italian tune up"!
Did the defective lambda sensor flag the management light at all?
It may need a few miles under its belt for the ecu to learn the new sensor.

I had the management light on for a good 6 months, literally changed the sensor just as I went to test and cleared the codes. I assumed it would need running in for a few miles. Im going to disconnect the battery to reset the ECU

 

[Splat90]

UPDATE:

Still not sure on what caused the readings but as I had a faulty lambda for months (making me run rich) I cleaned my spark plugs, which were pretty sooty. Ran some Redex and red lined my way to the garage. Passed with ease.

Also believe that it could have possibly has something to do with the crank case breather but this is something I'll check at a later date.

 

[Burnerman]

Can't beat a red hot cat mate! Check the air filter state when you get a moment.
John

 

[Splat90]

Can't beat a red hot cat mate! Check the air filter state when you get a moment.
John

Did a clutch job last month, did a standard service then, oil, air, plugs etc. I'd imagine it would still be ok!

 

[Spark123]

It could just be the amount of crap in the exhaust system with it running rich. Probably just needed the Italian tune up.

 

[Splat90]

It could just be the amount of crap in the exhaust system with it running rich. Probably just needed the Italian tune up.

I agree, the Redex was a more play it safe type of thing only put 20ml in to 10 litres didnt really want it in my tank anyway. Also quite tappy, think its my valves as there not hydraulic so didn't want to possibly ruin any seals with the Redex.