Air leak? O2 sensor? Bad idle when cold

Hi
2006 plate started to idle rough when cold start but fine once warm, it’s come up with o2 sensor faults but when checking for air leaks noticed this pipe isn’t connected to anything? What’s it for? No obvious air leaks so maybe in o2 sensor?
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I think that the hose you have is the gearbox breather and actually just sits open ended. Is the other end sat on top of the gearbox?

What are your fuel trims doing when cold?
 
OP
OP
G
I think that the hose you have is the gearbox breather and actually just sits open ended. Is the other end sat on top of the gearbox?

What are your fuel trims doing when cold?
Typically it’s just been ok and idling good, but trims are short trim 0.0 long -10.2
 
OP
OP
G
I think that the hose you have is the gearbox breather and actually just sits open ended. Is the other end sat on top of the gearbox?

What are your fuel trims doing when cold?
Typically it’s just been ok and idling good, but trims are short trim 0.0 long -10.2
 
I have had issues recently and it would idle ok then drop and struggle and then pick up again. I had no faults though. My st trim would hover around 0 then drift to - 25. The cl would.change to ol and indicate fault for a brief second then idle ok for a bit. Long term trim was -10. Rinse and repeat the above

I unplugged the second o2 sensor and idle settled down. I have since replaced this and idle is now smooth and problem has not repeated. Cant drive car just yet to confirm hesitancy has gone.

Some threads on the site also point to second o2 sensor causing issues and showing as sensor 1 on scanner.

If it happens agin it might be worth unplugging this as a test
 
OP
OP
G
Just done another cold test and idle was bad, trims were short -25 long -10.2 ? So short is 0 when good idle , bad idle -25. What’s this mean please?
 
Double post. Try disconecting the second o2. You need to get under car to reach it it sits where the exhaust lift over the cross member
 
Ok will give it a go , was it easy to swap if needed? Euro parts the best place to source a replacement if needed?
22mm spanner. Be carefull not to strip thread. Be really carefull not to cross thread replacement. Got mine from car parts 4 less. 710700435 denso version for 53.89
 
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