355 (slow down light warning)..concern - Ferrari Life
 
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post #1 of 12 Old 10-28-2006, 09:55 AM Thread Starter
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355 (slow down light warning)..concern

Hi,

My 20k 355 today showed the slow down warning light.. a bit concern about it and will get it checked..

referred to the manual and it could be related to the catalytic converter gases.. The car has a a tubi exhaust..

has anyone had any experience with this? any concern?
and can i drive it slowly to ferrari specialist?

tx for any feedback..

:drive:
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post #2 of 12 Old 10-28-2006, 02:50 PM
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Slow Down Light

This is a pretty standard problem on a 355. There are three thermocouples (TCs) in the exhaust system - one in each catalytic converter and one in the muffler. If the TC senses too high a temperature, it sends a signal to the computer which in turn sets the Slow Down Light. Theoretically, if you slow down, the converter will cool down. If the TC sends a "Really Hot" signal, the computer can shut down half the cylinders, which is really annoying, to keep from melting the converter.

Unfortunately, these thermocouples are also known to fail with great regularity. There's a fifty-fifty chance that there is nothing wrong with the engine, just bum TCs. The TCs cost $150 each, so it's not cheap to just throw in a new set. Furthermore, each TC's signal goes through a buffer which is also quite expensive, but not known to fail as often.

So, the big question is, is the light for real, or a false setting from a bad TC? One car I worked on, the light would come on 15 seconds after a start up, when the converter couldn't possibly have heated up that quickly. Have you seen this happen, by chance?

To be safe, I suppose you need to take it in, but be prepared to buy some new thermocouples. As long as the place isn't too far away, I think you can drive it. -Steve
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post #3 of 12 Old 10-28-2006, 05:21 PM Thread Starter
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thanks

thanks steve, for the advice. Will check it today and see what happens..

..and drive slow to the garage..

matt:drive:
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post #4 of 12 Old 06-05-2007, 07:14 AM
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what was the outcome. I am interested because I intend to purchase a 355 as well.
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post #5 of 12 Old 09-15-2007, 10:24 AM
 
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I had a similar problem where my left bank was shutting down 1-2-3-4 Slow down HuD warning.

I replaced the cats and the problem disapeared.

It now 5 months later and its Winter (Australia) and the prblem has re occured.

Same deal HuD warning comes up and the Left bak shuts down.

So you think its the sensors that are the culprit or could there be an other problem?
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post #6 of 12 Old 09-15-2007, 10:36 AM
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I had this problem several years ago on an F355 GTS. Turned out ot be a bad spark plug. Had it replaced and the problem disappeared.
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post #7 of 12 Old 09-15-2007, 10:45 AM
 
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Originally Posted by Boxer View Post
I had this problem several years ago on an F355 GTS. Turned out ot be a bad spark plug. Had it replaced and the problem disappeared.
Thnx for the quick reply Boxer.

That makes so much scense to me. I havnt been driving the car much at all latley b/c i am trying to sell it and the plugs are starting to fowl up. Already replaced them once looks like i need to replace them again

Thnx heaps
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post #8 of 12 Old 09-15-2007, 06:13 PM
 
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How can you tell the difference if its bad thermocouples or bad cats? Replacing the cats requires a bank loan!
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post #9 of 12 Old 09-16-2007, 05:44 AM
 
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How can you tell the difference if its bad thermocouples or bad cats? Replacing the cats requires a bank loan!
My mech did a temp test on the cats and the heat they were generating was in excess of normal op.

The left cat was pretty much finished and the right cat didnt have much life in it left.....(59,000km on the clock) so i decided to replace both at the same time....no point in wating for the right one to go as well and then double up on the work.
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post #10 of 12 Old 09-17-2007, 09:00 AM
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stav

i have the same problem with my left cat, i got the check engine light on and the obd2 results pointed to a faulty left cat and o2 sensor.

have you replaced them yet, the nj ferrari dealer quoted me at almost $5K just for one side just to replace the cat, o2 sensor and labor charges.

i am looking at aftermarket brands and i have narrowed it down to hyper-flow or tubi. unfortunately tubi is as expensive as the factory cats made by ansa, so i am leaning towards hyper while will give me about the same increase in mid-range horsepower of the tubi's which is about [email protected] 4-6K rpm.

it is getting cooler here now, so i may have all the work done, including a complete fluid change ealy spring next year to get ready for next years summer.

ps

did the mechanic have to take down the cats in order to examine them, if he did then you might as well replace them there and then in order to save from taking it apart again.

Chicago_Pete
hey slow driver
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post #11 of 12 Old 10-07-2007, 04:30 AM
 
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Hey Monza

Mech didnt have to take the cat off to do a Temp test ....used a laser temp gauge.

Also yea had same prob with the Price of the cats that you said.....however in Aust they cost $4k (AUS) each which is about $3.6k US each so its abit cheaper here.

I opted for aftermarket cats $2k each ($4k total for parts for both) which was half the price but for the life of me now i cant remeber the brand.
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post #12 of 12 Old 10-07-2007, 04:22 PM
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Hi Stav, I am opting for Hyper-Flow Cats, about half the price of the OEM.

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