355 M2.7 cutting , run on 6 or 8 cyl

I would start with your plug wires...they are a known weak area. Remove and inspect/test them. Or just replace them. Might pull the plugs too.

 

As the F355 ages it's possible to develop symptoms and causes similar to the 348 Motronic/ wiring problems. What you describe is classic 348 2.7 Motronic and possible cause/ solutions are well documented on FChat:

Grounds
Connectors
Wiring
Lambda sensor/ ground
Thermocouple ecu

In addition to the spark plug wires. A spark issue will not trigger an error code (though will on Motronic 5.2 and up) as the ECU does not monitor spark, only trigger it. If there's a malfunction down the line it doesn't have sensors to monitor.

Best,
Rob

 

I am pretty certain that all 355's have the later O2 sensors with a seperate ground wire, so are not as suspetible to the ground issue like the 348's.

 

Hi Dave, The 348 and 355 all have the same type of 4 wire 02 sensors, Frt 02 on 5.2, (different part no. becuase of plug ends and wire length). The grounding from I could see wasn't related to the 02 ground wire itself it was because the 02 wouldn't complete the ground so you would need to attach a wire to the sensor housing and then to the frame to complete the ground. The way Ferrari grounded the 348 electrical system is different from the 355, they used the female/male plug ends on the 348 which would get lose and corrode vs bolting the grounding wires to the frame as was done on the 355. Regards, Vern

 

In addition to what the other guys have said, check the condition of the connector wires for your Mass Air Flow Sensors. Also have a look at the condition of the wires for the cranks position sensors.

 

Thanks Vern, I stand corrected...but 355's ARE less suseptible to this grounding issue right? Because I have never heard of anyone experiencing a problem...but hear of it frequently with the 348's.

 

That is the way I have seen it too. It appears it was corrected with the better ground setup on the 355. When I owned my 348 and had seen the way they were gounding the electrical system I was surprised that they would do it using that female/male plug end concept your just asking for corrosion problems, always seems odd that someone with layman abilities(me) can see that and they couldn't. Regards, vern

 

Water in the plug holes can definitely cause ignition problems! I had the very problem with my 78 308 GTS anytime I washed it! The fix was to order new, fresh, tight fitting covers from T.Rutland's. Any Ferrari parts supplier should be able to help you with that. BUT, you should be able to see if that was the cause, as you will likely have a bit of rust or water/mineral residue on the exterior of the plugs...did you see any when you removed them?

 

Someone recently posted of a bad coil. Perhaps you should swap yours left, and right? See if the problem moves to the 1/4 bank.

 

Hi!
Also look for "Flywheel Grease" and "Slow Down ECU´s". Has been written down a dozed times.

Both can give you the same symptoms that disappear and resurface with no rules!

Please don’t expect the garage to know about these faults or even understand the problems! 99% of the professional mechanics only use the internet to look at extraordinary norks, never for technical support. International "don’t want to know" illness...

Have the compression checked too. You don’t have to remove the plugs, can be done monitoring the starter current!

Good luck!

 

Your crank sensor fault could be your clue. Many 348/355 owners have reported bad wiring connections inside the rubber cover of the harness that connects to the actual crank sensors.

I'd peel back those rubber boots and examine the wiring. A loose connection to your crank sensors will interfere with the correct firing of your spark plugs.

 

Hey.. i have the EXACT same problem with my 94 512TR that has the M2.7. I just had a major service done (timing belts, water pump etc) I had test pipe and performance muffler installed. When I drove the car the first day after the major, i got slow down light cyl 7-12.. and car run like terrible under 3500rpm. over 3500rpm.. the car runs perfect.

I brought it back to the garage, they disconnect the 02 sensors, and now the car runs fine.. but everyone is telling me there is still a problem, and the 02 sensor should always stay connected even if I have test pipe. I have been told that it might be Cam timing problem, or even maybe that there is an exhaust gasket leak.

 

i just went through this. Vern, what is the ecu on the left and right? toward the back of the engine bay. I changed the right side and all fixed.

 

I think you may be okay....are you reading the pins in the wrong order on the left?