A couple issues with my new-to-me F355

On the indicators, if they're all working they likely they were replaced with LED bulbs which have a different (lower) resistance causing the blinker to go faster. You could replace with incandescent bulbs or LEDs with proper resistance added in, cheap and easy fix, or just ignore it.

On the slow down light, you need to understand if it's real or not. Easiest way is to use an IR thermometer and measure the temp of the primary cats when the light comes on. If the primary cat on the side of the engine throwing the warning light is significantly hotter and approaching 700F, you have a mixture issue or misfire on that side of the engine causing rich mixture and the cat to get hot. If it's similar in temp to the other side, you either have an intermittent temp sensor or cat ecu issue, and swapping one or the other (cat ecu is easier) to see if the fault switches sides will help you narrow it down.

 

If I read you correctly, you said the car does not have cats. In that case the SLD would be some type of of malfunction. Could be wiring, cat ECU or thermal couple. You might type just unplugging and cleaning the connectors to the cat ECU. I wouldn't ignore it because it could cause a bank to shut down if it comes on solid.

 

If your car truly doesn't have cats, get rid of the entire SDL system (the probes and ECU's) and plug in the Technistrada dummy load plugins. I would still use an IR temp gun on various parts of the exhaust to make sure both banks are similar/same temp. But there is zero reason to have the SDL system on the car if you don't have cats.

https://technistrada.com/catalytic-slow-down-ecus/dummy-load-sdl-bypass---not-for-installation-into-vehicles-equipped-with-catalytic-converters

 

This is what I did and works great.

 

I'm guessing based on this: "catalytic converter bypass pipes, and miniature catalytic converters,"

That the secondary is straight piped and the primary has 'sport' high flow cats, in which case you'd want to make sure that it's not actually getting hot. It's likely a faulty system but that's the first check if you have cats on the primary.

 

SDL .
Seeing as it’s likely not been used prior to the auction , it could simply be old stale fuel ? Needs an old fashioned Italian tune up.
Run a few tankfuls of injector cleaner through it . Do IR thermometer the manifolds for piece of mind .
Contact clean the CAT ECU s ….

Then if the thing still flickers investigate the CAT ECU s as previously suggested^

Is it a early 2.7 , or later 5.2 motronic,?
2.7 have twin MAF s and air boxes , 5.2 s one central MAF and airbox for the filter .

The 5.2 s notorious for the main ECU that controls the engine in a bank detecting a sensors dropped out of parameter and cutting spark to a cylinder ……but NOT fuel . It’s this now inadvertent over richness of a bank that leads to excess heat and cracked manifolds ( how many 5.2 s left on OEM headers ? - ask yourself ) .Worse still if the symptoms are ignored the CAT catch fire .
You say it’s de catted and retro fitted with “ mini cats “ ….so iam presuming they are still connected as per OEM s to the CAT ECUs ?? Hence the flickering SDL .

If you have the earlier Bosch motronic 2.7 ( far more simple of fewer sensors ) you don’t get this partial temporarily over fuelling / enrichment issue found in the 5.2 , instead it far simpler the whole bank including fuel simply shuts down . So all 348 s and the early versions of 355 s don’t suffer from crack headers or CAT fires like the 5.2 355 s .

But the bank shutdown phenomenal can be irritating instead . But an easy get around is available.

 

They're up under the rear fenders behind the rear lights. You can follow the wire from the temp sensor in the cat to them. Reason I say they're easier is, depending on the cats you have, the temp sensors can be very difficult to remove without ripping the bung off (I learned that the hard way). If you put a wrench on the temp sensors and they easily come loose, they're easy to swap side to side.

 

The 2.7/5.2 ECUs physically can't shut down the spark to an individual cylinder (due to how the coil pack wiring is configured). The best it could do would be two cylinders, but why would it drop 2 cylinders in response to a "sensor" reading. Wouldn't it shut down a whole bank as it does with a cat overheat whereby the fuel is cut to the whole bank?

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The above text is not quite accurate. The ECU cannot shut off power to the injectors on a single bank. Power to all injectors 8 is provided by a single relay. To stop a bank operating, it would have to stop providing the injector firing signals (ground triggers).

 

What a marvelous car - my 296 was Monaco over Sabbia. Looks wonderful.

On my 1997 I had Fabspeed sport cats going to a Tubi and I could never get rid of the CEL - a reset would keep it away for a day or so, and then the "fuel/air mixture" error code would set it off again. You could hear and feel it was running fine, but for the slightly rich exhaust pinging the sensor. I miss my 355, way more than my 458. It had a simple charm and fantastic sound.

 

I'm going to knit pick you here Ian. Voltage to the injectors is provided by a single relay. No power until they are grounded and current flows. So technically the manually is correct.

Anyway, another possibility could be that the TC for one bank and the TC for the by-pass pipe are connected to the wrong TC ECUs. But this is most certainly a TC or TC ECU problem.

 

Julia,

Congratulations on a beautiful car!

In regards to the SDL......mine will come on when I start the car. It started out last year after driving it for a while to now it will come on 15 seconds after I start the car. What causes that is one of three ECUs which notoriously fail over time. Each ECU is around $450 new or $250 or so used. Mine are the original.

I will get around to replacing them (easy to do) this spring but it is a stupid problem to have. Checking the Cats with an IR gun shows they are stone cold......yet the SDL blinks.

 

Yes, that's a beautiful F355 Spider, Julia. Drive it in good health.

Barry

 

Julia,

I had all kinds of unexplained CELs and SDLs and then I noticed that on the last engine out the postcat and the precat O2 sensors were mixed up. The car ran but it was struggling to keep it controlled. The mechanics who were not Ferrari mechanics (Porsche actually) got them mixed up. After getting that straight the car now runs like a champ for over 3 years.

 

If one wants to be very technical, one can also argue that it is incorrect to say that "Voltage to the injectors is provided by a single relay". The single relay actually provides a "drain" for all injectors, towards the positive side, and the voltage (the current of electrons) comes from the ground, switched "on" by the ECU. When the ECU switches an injector "on", the current will flow from the ground, through the injector, and into the "drain" via the relay.

Only if the fact that the current flows from the ground to the positive side is taken into consideration, the statement in the manual that the ECU will "cut off the power supply" can be taken as correct.

However, if the manual is written following the generally accepted (although technically incorrect) "convention" that DC power supply comes from the positive side (from the relay in this case), and that the power flows from positive to negative, then the statement in the manual that the "power supply" is cut-off is incorrect.

 

John, I was assuming the 5.2 ECU only shuts down one bank for an overheat on one side. If it only shuts down one bank, it can't control the fuel injectors by removing power (via the single relay). The relay can only shut down both banks.

 

A very experienced tech informed me on the 5.2 cars situations can and do arise whereby they loose spark ( for what ever reason ) but continue to inject fuel , while the bank is operational .This I think can occur on one jug or more .
It’s in these circumstances you get the over richness leading to manifold / header overheating = cracking or further down the line the CATs overheating leading to fires in 355 s , because unburnt fuel is dumped into the headers

If I understood him correctly ( discussing the differences between 2.7 vs 5.2 ) with the 2.7 the whole bank shuts down the fuelling if over rich ness ( for what ever reason ) or the CAT ECU s , or it’s sensors go bad is detected . Each bank on the 2.7 s has its own separate fuel relays and engine maintenance ECU s they work independently. So you can get a bank shutdown. Kinda limp mode .

Where as with 5.2 the one relay for both banks can’t shut down a separate bank and keep the other running if there’s a problem with loss of spark for example the fuel just keeps washing through unburnt .

So with 2.7 s if any excess excess unburnt fuel gets through it gets detected by the CAT ECU sensors and that bank is shutdown so you don’t get cracked exhaust manifold s / headers . Something like that ?

This is the jist of why 5.2 s crack there headers and / or can set on fire .
Therefore it’s worth retaining/ maintaining a fully functioning CAT ECU s with the SDL system on the 5,2 s , and trying not to drive too long with the SDL illuminated.



I might be a bit short of the electrotwackery technicality but there is a difference in favour of the more primitive 2.7s .

 

Ah, I see what you mean. My definition of "power" is the 12 volts provided to one pin of each injector when the key is turned on (with the multimeter providing the ground).

You could get bank shut down if the 2.7 stopped providing a ground for 4 injectors (and I believe the 2.7 and 5.2 ECUs do use this method). If you tried to shut down a bank using the respective injector relay, the CAT ECU and the CEL/SLOW DOWN lightbulbs would lose power. That doesn't make sense.

For info: Power would also be lost to the fuel pump (if fitted to a particular bank), the MAF, the idle speed regulator and one of the evap valves. Also, the ECU would lose power on pin 37 (whatever that does).

 

glad you've got the indicators sorted.
On the SDL, assuming the car is running fine (which you'd know given you own another one) then fuel and spark are probably fine. Worth checking with the temp gun as others have said to check its not overfuelling, but again you'd likely hear it running rough. I run no cats in mine and it doesn't generally trigger the SDL unless I'm driving the doors off it on track.
The 5.2 just has the one light, so you can't easily tell which bank is the culprit, however the CAT ECU's are prone to water ingress and then throw a wobbly, so try swapping them out in the first instance.
The left hand one is easy to get to, the right hand one more fiddly but easy enough. Plenty of google images showing you locations.