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

Took the car out for a drive this afternoon and got to the first stop light (maybe 300 yards) and the idle began acting erraticly...as I tried to pull away it felt like I was driving on 1 cylinder and kept wanting to stall out.

CEL 1-4 and Slow Down 1-4 came on. I turned around and limped home...I was *barely* able to climb a small slope in my driveway.

I ran the diagnostic and got code 1121 which translates to RPM sensor.

Ok, now what?? Where is this sensor and how can I go about trouble-shooting? I suspect a wire is loose or dirty connection. The car has run flawlessly for my 10 months of ownership - never so much as hiccuped.

NOTE: The irony of the fact I just bought the gold connector kit and am planning a major in a week is not lost on me.

Aack...just figured out I need to check for more codes. 1121 is a red herring. BTW, is it possible to get more zany posts on this thread?

 

Nobody has a problem until they have a problem.

 

LOL...and your keys are always in the last place you look. Let me know if you actually have some useful advice.

 

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

 

Yes, but if you want to maximize performance - always remember to wear your tinfoil hat. You probably need to wear yours at all times just to be safe.

 

Catalyzer temperature ECU.

Ideas on how to troubleshoot. Just got done looking for loose/dirty connections - nothing suspect. Cleared codes and now going to let it idle for 15 mins.

Could be a bad ECU I suppose...

 

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.

 

Thanks Huge. Dumb question but where is cat ECU? I just checked literally all connections I could find on passenger side (bank 1-4).

 

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

 

I useless, not useful

 

ahhh yes...good times.

 

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!

 

Sooo...what are you doing today Eric?

I didn't leave ECUs disconnected but did reset the codes/cleared memory, let it idle 15-20 mins, shut it down, restarted and went putting around the neighborhood in 1st and 2nd. No issues, behaved normally.

Thanks Dave! Nope, never got out of 2nd gear and car was stone cold.

Ok, I'll admit it right now - I am a bit dense and cannot tell you what the ECU looks like. I followed all the wires but am unsure which part(s) you and Eric are asking me to disconnect and/or replace.

A parts manual picture or actual photograph would help me tons.

 

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

 

Thanks, that's a big help.

So, dumb question - if I'm driving and the car throws this error again, can I just disconnect the offending thermocouple that goes into the ECU and carry on? I'm hoping to drive the car about an hour up the road this evening with my wife and the last thing I need is to get stranded.

 

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?

 

2 reasons:

1). I'm a bonehead and was checking the wrong bank at first.

2). That code is totally normal/expected if the engine is off when you pull codes.

All part of my continuing education.

 

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.

 

Thanks Dave...solid advice for me and anyone coming after me with similar issues. Whatever is going on here with my car will be addressed properly.

My intentions behind the question were only to understand if I could disconnect it in an emergency. If it throws this code again and I believe it is 'erroneous' - I want to be able to get back home. The car drove like an absolute DOG when all this hell broke loose. Thank goodness I was so close to home, I could have pushed it home if I had to.

My ECU is not discolored. It looks sort of like a glycerine bar of soap - a translucent yellow/green (didn't see any black).

I plan to monitor it closely over the next week and probably will swap ECUs to see if the problem crops up on the other side.

 

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.

 

I swapped the CAT ECUs. Will drive it daily for the next week or so and see what happens.

I took some pics of both the one that threw the codes and the one which has not. The surprising thing is that the one which threw the codes is the greenish color and the one which is acting normal is black. From earlier posts, it sounded like green=good, black=bad.

3forty8 - does your spare CAT ECU look like this, have the same markings? I may take you up on your offer. I'll release your Stooge's Rule spanner for a new/used ECU.

 

greeny...
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blackie...
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