HELP....failed on emissions!

[Cowie]

Just took car in for MOT and it's failed on emissions
result: CO <=0.300% (actual 0.724%) and second fast idle test gave (0.435%)
lambda is ok 0.970-1.030 (1.018 actual)
I do get emission light on now and again with the blue flame and on vag-com it throws up this code
16804 - Catalyst System: Bank 1: Efficiency Below Threshold
P0420 - 35-10 - - - Intermittent

Any idea what i can do to get it through
cheers

 

[Gordz]

What just squeezed my ibiza through once was just absolutely ragging the car around at high revs for about 30mins before the MOT, also chucking additives into the fuel (like redex etc), and got the garage to test the emissions straight away.

That worked for mine, and I was well over the emissions (can't remember figures) first time round. But just scraped through after doing the above!

 

[Cowie]

gave the car a good run

 

[andycupra]

what fuel you using?


blue flame run a 100 cell cat which doesnt give much room for manouver.

 

[Cowie]

BP ultimate,is only stuff round here,will some additive help?

 

[adam cupra 20vt]

Does that code not mean the 1st lamnda is faulty and this would cause it to over fuel?

I think bank1 is pre cat? its usually bank2 that comes on with a de cat if its the excessive flow?

I may have got that wrong, just an idea

 

[Cowie]

so a faulty lambda then adam?
can i do a check with vag-com to tell this?

 

[adam cupra 20vt]

16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

Possible Causes

Leakage in Intake and/or Exhaust System
Catalyst faulty
Oxygen Sensor(s) faulty
Oxygen Sensor(s) Control faulty

Possible Solutions

Check Intake and Exhaust System for Leaks
Check Catalyst
Check Oxygen Sensor(s)
Check Oxygen Sensor(s) Control
Perform Oxygen Sensor(s) Aging Check



I'm not sure what that check is all about? guess you do that with vag-com?

 

[DPJ]

so a faulty lambda then adam?

I'd say so. Front one.

 

[Cowie]

ok Dave is there a test i can run through vag-com to confirm this?

 

[PlatinumR]

Check the maf readings using vagcom on a run

A misreading maf can give this message as the engine is trying to get the fuelling right but the airflow is wrong for rpm, throttle position etc giving bad burn and bad emissions causing the 02 sensor to go nuts giving you the message.

Bank 1 pre cat, bank 2 post cat (only an emissions warning of a bad cat, no effect on engine control, normally mapped out on stage 2 cars)

I would expect to see the lamda reading well out if it had failed but it is fine.

How is your mpg? also a good indication of underperforming maf plus how clean is your air filter?

 

[cpentney]

I have the engine light on mine and the same fault code as above. I've had a new Oxygen sensor fitted but the light has come back on.

Rang dealer today and was asked if I've replaced the Cat, which I had was last year. They then said that non SEAT cats can cause this issue as they simply don't work. Mine's an early Leon and this problem is quite common apparently. Can anyone verify this? They said that a SEAT cat would be about £665 fitted , so obviously don't want to go down that route unless absolutely necessary. Any ideas?