348 strange behaviour

Just because you don’t have a cat doesn’t mean that the cat temp ECUs don’t need valid data and can’t go bad themselves. It sounds like that’s the issue.

Did your mechanic pull the codes?

 

Some of us are the original owners of 348's and chased these 348 ghosts from the day they left the factory. What you describe is a typical intermittent failure caused by poor electrical connections.

 

All my intermittent problems went away when I replaced all the relays.

 

Does he have a Ferrari SD1 tool? The ECUs should be detecting and recording faults.

If you can at least identify the bank which is shutting down, you can always swap components from left to right. I will never understand why many Euro Ferraris don't have SDL and CEL warning lights.

 

There are solutions to chronic ghost chasing:
1- unplug/replug to refresh connections (with or without bending of pins to increase contact pressure)
2-electrical contact cleaners (with or without bending of pins to increase contact pressure)
3-contact enhancers like stabliant-22 and de-oxit gold (with or without bending of pins to increase contact pressure)
None of the above works for long but cheap and easy while inconvenient.

4-partial and complete re-pin of harness with pins/connectors/boots/seals/
This has been a permanent solution for many but is highly controversial as to what pins to use, whether this extreme measure needed, what it does to car value.

 

I have had similar problems with my 355. Once it was a bad coil which would intermittently cause 2 cylinders on one bank to die resulting in loss of power and change in exhaust tone. The fix was to replace the coil and the power module just to be sure.The other was a broken wire at one of the crank position sensors. At a certain RPM the vibration would cause a loss of contact and it ran like it hit and rpm limiter. Back off the throttle and it would run fine. That fix was repair the broken wire. There were no codes in either case.

 

My car too occasionally suffers from this syndrome. As best I can figure it, the problem only appears after the car has been sitting for awhile and definitely goes away once it is properly warmed up. Driving it weekly seems to avoid or minimizes its appearance. I have chased this ghost for years. As much as I can tell, it has to come down to wiring since I pretty much replaced or serviced everything else. Our TCUs are pretty simple devices so their failure isn't likely. I need to swap my ECUs but I sincerely doubt these are the cause since I have 4 and have rotated them around before. More likely, as FBB suggests, it's either wiring or pinning. My issues seem to affect only the 5-8 bank. One day I'll repin the damn thing. My short term recommendation would be turn off the power and pull your ECU 50+ pin connector, then clean the contacts on both ends as much as possible. It's easier to actually remove the ECUs from their location behind the seats to do this. Apply a contact treatment. Then drive the car more often but make sure it's pretty warmed up in the driveway first.

 

Did you only disconnect the probes (the Thermocouples) from the Vescovini Centralina or also disconnected the Vescovini from the car harness?

If you leave the Vescovini still connected to the harness, it can cause bank shut-down if something goes wrong with it. It is better to completely disconnect the Vescovini and this will not affect the engine running at all. You will only get "silent" code 4121 but no CEL or SDL.

 

It's 55-pin Bosch ECU connector.