Emissions problems - High CO on idle

Help. My car is runnig a bit rich on idle. When reving through the range the emissions are spot (0.3%) on but on tickover the CO emissions are at 1.5% (allowed limit 0.5).
It would appear that the ECU MAP has a bit of extra fueling dialed in for the over run/idle as the exhaust manifold had actually burned through near the gasket on the #3 cylinder. I got through the NCT last time but this time I can't get the idle CO down and am now thinking that the test centre might have skipped the idle test as it was a retest for emissions and they were under pressure..

Any ideas anyone? It was hunting on tickover a few months back but has been perfect lately.

I bought a replacement 22B MAF from the UK but when I plugged it in the car wouldn't even start so that's gone back..

Do you think I'll have to get it remapped?

throw it on a diagnostic machine and get the parameters on the engine sensors.....
if the manifold was drawing in air ....the ecu might enrich the fuel mixture more to help that cylinder burn better.....
not really sure though :dunno: :dunno:

Had it on a diagnostic and it was inconclusive really?

Sounds like a lambda sensor, but it usually gives a code. MAF's sometimes do not give a code, even if there gone. How is the car driveing. Check for any air leaks in the exhaust system also. If all seems ok, I would replace the lambda sensor.

John

[quote author=johnny99 link=topic=7389.msg87522#msg87522 date=1211436557]
Sounds like a lambda sensor, but it usually gives a code.
[/quote]
I put a new one on for the last test but no harm trying that again.

[quote author=johnny99 link=topic=7389.msg87522#msg87522 date=1211436557]
MAF's sometimes do not give a code, even if there gone. How is the car driving.
[/quote]

Seems to be a ok, possibly a bit down on power? To be honest it's hard to tell. Running fine and tickover fine but I do feel that there's a bit less urgency on boost but then again I could be just used to it..

[quote author=johnny99 link=topic=7389.msg87522#msg87522 date=1211436557]
Check for any air leaks in the exhaust system also. If all seems ok, I would replace the lambda sensor.
[/quote]
Just installed a new manifold (required removing turbo etc) so that's all fine now.
I'll double check for air leaks but someone on the 22B forum suggested I disconnect a vacume pipe on the inlet manifold to cheat my way through the idle test? What do you think?

if ur going to disconnect any vacuum pipes...better of puttin a ball bearing or something in the pipe and refit it....doesnt look as obvious..this will affect the Map sensor reading thou
personally dont think it will work
good luck