Rich on Bank 1

Vacuum.leak ..

It seems it is affecting both banks so maybe manifold to Pentium gaskets


Maybe a smoke test or using propane method may reveal something

When you switched maf from one side to the other what happened

Wait ..i see negative value on bank 1 so my explanation refers to passenger side ..

The coolant sensor can cause dumping fuel
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Bank 2 has no coolant temp sensor, so -40C is normal. There is a temp sender for the gauge.
Bank 1 has no AIT (air intake temperature) sensor, so -40C is normal. The sensor is on the RH manifold, but it's wired up to the LH ECU.

Data is shared between banks, of course.

+1

 

Driver side ..bank 2

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Test 1

Tell us how short tirms change from idle to 2500 (steady)

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Does the tool say that it has achieved closed loop

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I find that inspecting the spark plugs of modern engines like a 550 is ... inconclusive. Since it costs the same amount of labor to remove and inspect versus remove and replace, I suggest you put that factor to bed by replacing the spark plugs on the car. All 12.

I don't work much on 12 Cylinder engines but I have done a lot of misfiring and bank running rich on one bank of V8s. I can tell you that O2 sensors are ... rarely the problems. They just report the problems.

A dead or half dead spark plug will cause this. The cylinder does not fire, the O2 in the air is not burnt off so it shows up in the O2 sensor as extra oxygen (the sensor does not read HC, just O2) and it thinks the mixture is lean (too much O2). The computer then adds more fuel to make it less lean. That fuel does not get burnt completely because the cylinder is dead and it ends up in the cat overheating the cat causing the cat to glow red.

A minor air leak at the O2 sensor attachment also causes the same thing. Tiny little air leaks cannot be found by a smoke test. You have to find it visually. But tiny little air leaks can affect O2 sensor reading.

A bad knock sensor can also do something like that. Check to see if it is cracked, or impaired in some way.

Oh yes, there was this one time when the cam timing on one bank is off by 6 degrees which caused the engine to run hot on that side... Fun stuff. Let's hope you don't have that. You should check compression of the 12 cylinders and compare one side to the other side. That tells you something about cam timing. You might as well check compression while the spark plugs are out.

Finally, your long term fuel trim tells me you have problem on bank 2, as well. Good luck.

 

Good point. Sorry, got my negative and positive trims mixed up.

Mitchell, if an exhaust leak before the O2 sensors adds air, wouldn't the mixture be seen as lean, so the ECU has to add more fuel. Isn't that a positive fuel trim?

 

When I referred to vacuum leak I was address the positive 25 precent .. as Mitchell basis there are two problems ..one bank is lean and the other is rich .. I was addressing the lean condition which shows up as a positive furl trim



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This thread:

F355 Head Scratcher | FerrariChat

is the exact version of this problem in a 355.

 

The fact that it's been four years since the last belt replacement is more likely that the timing has drifted out of spec for whatever number of reasons (stretched belt, loosening tensioner bolt, tensioners) so you should really look into that. Also this very symptom (glowing red converter on one side) was present on a V12 (456) that belongs to a moderator on here a couple years ago and it came to cam timing issue.

 

See this thread, move down to post 16 and 17.

People still need to be taught this I guess | FerrariChat