F355 2.7 with CEL 1-4 & Slow Down 1-4

Nobody has a problem until they have a problem.

 

Is it a myth that these cars run better with the more articles of Ferrari gear one is wearing while driving?

 

Rick,
search the threads...there is a ton of info. Bottom line, 90% of the time, there is a failure in the catalyst temperature monitoring circuit. Only Ferrari and Maserati feels the need to use this frustratingly unreliable and largely useless system.

Basically you have either a bad cat ECU (most likely) or a bad cat temp probe. The only other remote possiblity is a dirty connection/plug or other wiring problem. Start with the obvious, which is the cat ECU. If only on one side, try swapping the ECUs and see if the problem moves. Also get out a can of electrical contact cleaner and a stiff toothbrush (or the M16 extractor brush that Dave Helms provides with the gold connector kit) and flush, brush and flush some more, each connection in the circuit.

 

http://www.ferrarichat.com/forum/showthread.php?t=288460&highlight=tinfoil&page=6

 

I useless, not useful

 

Hmmm, yes, sounds like some flakey cat ECU trying to tell the Motronic that it is overheating and shutting down one of your banks. I *believe* on the '95 355 (2.7 system) it is like the 348 where you can disconnect the cat ECU from the wiring loom and prevent it from shutting down your bank.

I have a spare cat ECU you are welcome to, but even though the guts are the same I think the connectors might be different between the 348 and 355. Try disconnecting your cat ECU on the offending bank, reset the computer, go for a drive and see if the problem persists.

 

Follow the steel braided temp probes from the Cat to the brackets holding the Motronic ECU's in both rear corners under the fenders.

Unless you were bouncing off the rev limiter in those 300 yds there couldnt be enough heat to generate a REAL cat over heat condition. Disconnect the Slow Down ECU's and go for a drive around the block a few times, shut it down and reconnect the SD ECU's and see what happens. Upside is you have the parts in hand to fix it.... no better time to knock off the two plugs on the front crank pulley if they are a problem at this time.

The whole gang wearing the foil hats... Hang your heads any lower in the engine bay and you might find a new method to test plug wire insulation. I bet that would have the neighbors talking!

 

http://eurospares.co.uk/partTable.asp?M=1&Mo=691&A=1&B=40970&S=

Part #69.........has plug in and plug out....should be mounted on the cradle(?) under the top shield. Oh heck a 2.7 what do I know..lol

 

I could really get into a long winded deal of cause and effect on this subject, but the end result would not answer your question.

I defer this answer to someone who is running cats and has left the OE thermocouple system in place.

 

Rick, why did you say code 1121(rpm sensor) was a red herring?

Did you replace this sensor?

 

Disconnecting the larger plug to the slow down ECU should be considered a test situation, not a solution. The problem we have is all of these safety circuits get disconnected based on assumptions they are bad.... we need to be able to assume they are warning us of a real problem. Ignoring the CEL's and Slow Down lights is what is leading everyone down a long and ugly path.

One has to view each of these problems in an analitical manner. Can the current situation bring about a 'real' Cat overheat condition? Stone cold, acceptably smooth idle, 300 yds at low RPM without a 15 min idle period just prior.... No, not very likely the Cats would be overheating given those conditions. Given those parameters the next most likely situation is a failed SD/ECU IF the potting material is black and not Green on the ECU itself. We are now starting to replace some of the green ECU's but as a rule they are quite reliable. There are about 6 other failure modes that will bring about the same conditions but one can not assume, you have to check and verify each step.

Once each of the following is verified, smooth running condition, black potted SD/ECU's, failure mode under unlikely conditions, disconnecting the SD/ECU eliminates the bank cut out problem, both Cats look the same without any visual evidence of overheating (one shiny and one gray in color), no rattle from the Cats indicating a matrix breaking apart.... Sure, I would disconnect the larger plug to the SD/ECU and drive it. Drive it based on assumptions alone? Nope, that is what is destroying these engines and the risk/repair cost ratio is too high for my personal budget. We have to be able to believe what the warning lights are telling us and THIS is what I have been working to do.

 

After the great job I did tightening the hoses to your overflow tank you sure you want me touching your car again??? I'm free later this afternoon if you still need an extra pair of hands, LMK.