My first mystery electrical problem has manifested itself after 41/2 years of happy driving (not bad for an Italian car !?). Car starts perfectly, 'Slow Down' lights on dash illuminate for a few seconds on turning the ignition then go out as expected. Initial few minutes of driving is perfect however when car warmup is nearly finished, or at least after driving 5 - 10 minutes or so the engine goes into 'slow down' mode. I loose significan power, the exhaust note changes and it sounds like it is only on 4 cylinders istead of 8 yet your still able to drive all be it slower with no power. So far it only occurs briefly. A couple of times all I did was give it a squirt in neutral and full power came back but the 'slow down' period is getting longer. Today it happened and lasted a few minutes of driving until the enigne came back to full power and I am getting a little nervy about it. I don't want to get stuck k'ms away with a full breakdown. Now for the BUT !!! ..............neither 'slow down' light comes up on the dash so I can't tell if it 'is' a slow down problem or what bank is being effected. But I'm 99% sure it is a slow down fault based on what happens to the engine. Could it be a loose or oxidised connection that becomes effected as it warms up. Can anything else cause this. I have already unplugged and replugged the thermocouple connectors (next to the coils) a couple of times but to no effect. Any other connections that might need attention...!?!?
Morning Red. Not sure if it'll help given your location but I had pretty much the same thing happen on my 348 shortly after buying her. Intermittent slow downs and banks cutting out. I spoke to a Ferrari mechanic and he said it could be all sorts but damp getting into the system over a period of time can often cause it. My car now lives in a drier atmosphere (dehumidified carcoon) and that sorted it out right away. Now have the system deactivated after fitting high flow sports cats but thinking about having it plugged back in at some stage.
Thanks for that......hmm can't say that its very damp here and we are in the middle of a hot summer and today in particular is 26 C with a dry northerly wind. Also forgot to mention I have no cats just test pipes with a tubi (awsome sounding !)
...did you get the 'slow down' lights come on when it happened. In my case no light comes on ?????!??
Started with flickering slow down lights, then now and then steady slow downs, then slow downs with rough running, finally cylinders cut with no lights. Regarding the damp, obviously you're in a nice part of the planet, but what's your relative humidity during the day? If warm relatively moist air seeps into the system, when it cools down at night it'll condense inside the system. Over time it could build up? Just a thought.
... Hmm possible. I guess only time will tell although i do try to use the car every weekend or so. except over winter where it isn't possible. You see my car is allergic to rain. It breaks out in a rash if it gets wet it hasn't sat around for long periods without use ! Maybe a nice long run is needed to dry everytning out thoroughly !!
Andrew, if you have removed the cats what did you do with the sensors that are there to protect the cats from overheating to initiate a "slow down"? Perhaps your ECU is somehow interpreting a signal from your sensors (or has a fault)?
Probably a faulty cat ECU issue. Switch the CAT ECUs from the right and left side and see if the light flicker swtiches sides on your instrument. If so, you need to simply replace that faulty Cat Ecu. If, after switching, the light remains on the same side, the problem is in the CAT itself. The whole swtich and test will take you less than 10 minutes
... The cats where replaced by test pipes prior to my ownership however both O2 sensors and Thermocouple sensors are still in place and for the last 4 year shad no problems !
... this is the mystery at the moment that when it happens I get no lights coming on at all even that both the slow down 1-4 and 5-8 come on when you first turn on the ignition, for a few seconds, then go out as expected... !?!?!!? So I don't know that swaping the ECU's will tell me anything more at the moment.
The most likely connection issue would be at the CAT ECU (properly called a signal amplifier). where the thermocouple plugs into it. These are under each rear fender above and behind the rear wheels. After de-catting my car, I removed the thermocouples from my 95 and simply shorted the two poles together and have never seen a slow down light since! (I used two old dead thermocouples and cut the wires back, near the connector and soldered them together then plugged the connector back into the CAT ECU). Don't know if this would work on a 5.2 car, but its fine on my 2.7.
I didn't personally fiddle with it, but I am pretty sure it was the connections to the sensors as per above post
You said the cats are gone and you have test pipes instead? In that case where are the themocouples screwed into? Are there fittings for them in the test pipes? I may be way wrong here, but I believe the thermocouples are there to monitor the health of the cats. If the cats are gone (someone else chime in if I'm wrong) then you don't need the thermocouples. I'd pull 'em out and cap the fittings they were screwed into. Tie the thermocouples to the frame rails with plastic zip ties and see if that fixes things.
Thanks guys, you given me several things to check on so I will get into it on the weekend and let you know what happens.
....so its a 92 348ts. I will have a play on the weekend. Try uplugging and reconnecting the thermocouples at all connection points I can find. Then see if the problems comes back. Still bothers me however that I get no warning lights at all come up on the dash when it happens yet they come on with ignition so I know the globes are OK !?
