Quote Originally Posted by seanmul
I'm very curious, who told you to change the CAT? It's a bit drastic.

High Lambda= a hole, you'll find it hard to find as it's one that's sucking in air, it's called a venturi, the exhaust flowing at speed will suck air in any holes, see your results..the Lambda increases when the REVs to, (or speed of exhausted gasses)
your HC is very high for a new CAT, are you sure it was at temp? CATs burn off HC when they are at temp(and working).

Normally, to fix the HC on an aging BM,
remove and thoroughly clean your air intake, ALL of it. The throttle will have heavy deposits of burned oil, like TAR. On the manifold side so it needs to come off......
put in a new air filter.

After that and putting it all back together, you have to look around for an air leak, unmetered air will cause havoc with the air/fuel mix.
Go after your rocker cover breather pipe first!

Temp sensors are also a killer, it'll not show on any static diag, only a dynamic one.
Just change them, about 20-30euros for 1.
The cat that was in it was empty, Cat is a new MotorFactor job and car was driven hard for 7/8 miles before checking results so was well up to temp.

Seems to be a slight smell of petrol sometimes when it's running?


Thanks for the help BTW!