F355 Slow Down 5-8 Blinking Light and Rattling

Do you have the manual?

That is the indicator of an over heating catalytic convertor.

Could be a number of reasons.............

 

Well, I'd guess that a temporary rich start up condition dumped too much fuel, which then after time burned and cooled to within allowable temps......

I have heard of sensor failure causing problems in this manner but I'd not assume that...did it happen more than once?

Where's your Boxer?

I'm a carb'd 308GTB x 2 owner, what do I know??
I avoid catalytic converters if AT ALL possible.....LOL!

The rattling????? Anyone else??

 

It does just say "Slow down" after all.!!!......but I think you're supposed to follow up with investigation, as you are doing........

 

How old is your car? Have the cats ever been changed? Sounds to me like your cats have given up. The rattling could be pieces of it breaking off. The cat sensor could also now be broken too.

I was on the way to the garage to have my cats replaced (making a right old clanking sound) and got stuck in traffic. The slow down light came on. Went out again once I got moving.

Have your mechanic check the cats but be prepared for the worse. If you do have to change them, don't bother ith the OEM stock ceramic cats, go for the Hyper-flow ones. Cheaper and better built, plus for flow rate.

 

Usually when the cats are going bad they separate from the knitting that holds in place in the exhaust chamber. The ratteling is an indication that the cat substrate has come loose and will eventually break into pieces. I would not drive the car in this condition and have it check by a technician. Probably the only way they can tell if it is the cat they have to open it up and test it. Good luck!

Edit: Just read your last post. I am 100% sure it is the cats due to loss of power after 6000 RPM. The substrate has come loose and probably rotated inside the chamber and has partially clogged the exhaust passage. DO NOT DRIVE THE CAR...you will damage the engine from excess back pressure and excessive heat built up in your manifold.

Whoever replaced the cats did not do a thorough root cause analysis and unfortuantely, the root cause(s) whatever they are...caused the new set of cats to go bad again.

 

Take it to a mechanic with an sd2 before you burn all your exhaust valves.

 

In the first post higgins says that the rattling noise is in the right front of the engine compartment the cats are on the right and left of the BACK of the engine compartment.In my opinion it is ether the sensor that reads the cat temps or the cats are doing there jobs and there is something causing a rich run which is supplying the cats with lots of un burnt fuel, the cats heat up ,as the fuel is burning off,then the sensor dose it's job and the lite comes on.
4i2fly he did not say that there is loss of power at 6 grand he said the slow lite comes on ,so it leads me to feel that lots of unburnt fuel is coming into the cats as the rpm get up there .I think that it is not a cat problem but as I said a sensor problem or something is causing a rich running condition ,the rattle could be another problem altogether
my 02 DAVID

 

I must be dyslectic, you are right about the loss of power. I don't know why I read it as such...

 

You could try it ,,but if you are not going through lots of oil and if your fuel mileage is as it has been in the past than I would be inclined to think it is a sensor that is a bit sensitive.We can guess all day long at this but you need to get it to a good Ferrari guy for proper testing.I see you are in Europe how is your winter this year we are having a blizzard hear in cape cod ,20 to 30 inches of snow predicted and winds 60 to70 MPH,the 355 will stay in the garage for some time to come ,good luck with your Slow down lites
DAVID

 

Is the rattling still there? Is there any grey powder/dust in the exhaust tips?

 

then it does not look like it's the cats...

 

Get a emission check done this is a quick and easy way to see what gases are exiting the tail pipes,then take it from there,

 

I doubt that this will solve your troubles....one must ask, WHY did the fuse blow? It will probably blow again, until the fault is found...but at least you may be closer to a solution.

 

The air pump fuse blows because it is not a high enough amperage from the factory. This was a common problem. Replace with a 25 amp up from a 15 amp