355 2.7 high HC & O2 before cat

Checked the exhausts at 45000 km before engine out for belts and found the following values after cat:
CO 0,07 Right & 0,08 Left
HC 20 R & 27 L
CO2 15 R & 14,9 L
O2 slightly above 3% L & slightly below 3% L
As the O2 was high, we started to check the values before cat and it shows the right cylinder bank delivers high HC-values, even before and after switching ECU:s and automatic calibration. Also computer check is used and nothing special has showed.
As next test we are going for a leakdown check and possible engine renewal.
I wonder if someone has seen this before and have something to add to the list of possible faults?

 

Were the measurements done with the O2 sensors connected or disconnected?
If they were connected, are they working properly and were the ECUs working in closed loop?

 

Eric; Can´t really tell you right now, I will check with the workshop when I talk to them next time. I have just got the figures from the workshop, but I got to ask why you ask the question? Don´t misunderstand me, I´m just curious!

 

I just wanted to try to separate the problems, between an internal combustion problem or an engine management problem.
A closed loop control by the ECUs with bad O2 sensors can lead to an over-rich mixture. I think that for this basic control it is better, in a first attempt, to run the engine in open loop (without O2 sensors) and thus with the standard fuelling map.

 

Thank you for the explanation, I´ll check this with the workshop. My car is in the hands of a very experienced f-man, but he have never seen this before. It looks like he has tried many things, but he haven´t been able to spot the problem yet.