Slow down light flashing!!

The slow down light means one or both sides of the catalytic converters are overheating. This could be a major problem, something minor, or could turn out to be nothing. I would start by plugging in an OBD2 reader and see if you are getting any codes.

thanks Travis,

but what can cause the catalytic converters to overheat? and when you say major problem do you mean they need to be replaced or the Engine is causing the overheating?

i don't have a OBD2 but i will get one soon.

thanks

The pre-cats (the front ones) overheat because they are a poor design. They are integrated in to the header which allows the car to meet a cold engine smog test but they fail prematurely and cost a fortune to replace. Running the car hard causes these cats to heat up very fast. The slow down indicator comes on as a warning to prevent the cats from overheating and the packing to then breakdown. If that happens you have a real problem as the packing could clog your main cats (farther downstream) or worse get sucked back in to the engine under a backpressure situation.

If the situation persists it will cause engine misfires, the ECU to put the car in to limp mode, and eventually the packing breakdown as described. The only permanent solution is to de-pack the pre-cats.

so looking at the exhaust system diagram:

http://www.ricambiamerica.com/parts_catalogs.php?M=MA&P=&V=diag&I=3795

i see only one set of Cats (#1 and 2 in table).

flashgordon, when you say pre-cats you mean these right? and how do you de-pack them?

thanks

The diagram is a bit misleading because the pre-cats are not identified seperately.

#2 are the main cats - that is all that is needed to properly operate the car and meet normal emissions standards.

If you look between the arrows marked #1 and #3, you will see a flattened cannister integrated in to the header (just to the right of the gasket marked as #3). These are the pre-cats. To de-pack them, the tech cuts a square access hole in the bottom with a grinder, digs out all of the packing using a pick, and then welds the access cover back on. The downstream O2 sensor (located immediately behind the pre-cat) is then re-located to behind the main cat (this requires a longer sensor wire).

The slow down light can also come on if there is over 50C difference between the cats... this can be cause by many things including cat temp ecu failure.

ramich said:

thanks Travis,

but what can cause the catalytic converters to overheat? and when you say major problem do you mean they need to be replaced or the Engine is causing the overheating?

i don't have a OBD2 but i will get one soon.

thanks

Click to expand...

There could be a number of things that make the slow down light come on. Don't jump to any conclusions until the car is checked out. It could be something as simple as a bad sensor.

Note that this should be covered under the 8 year US emission warranty, assuming you haven't altered anything from OE spec that could have caused it.

http://www.epa.gov/oms/consumer/warr95fs.txt

Maserati's policy on this usually seems to be that they look for any scrape, scratch or dent and try to say that the bump or vibration loosened the material and caused its destruction. This is one issue that they seem to have difficulty stepping up to the plate on.

I'd definitely have a look under there and inspect them yourself before taking it in just to see what kind of shape you're in.

FormulaDynamics said:

Maserati's policy on this usually seems to be that they look for any scrape, scratch or dent and try to say that the bump or vibration loosened the material and caused its destruction. This is one issue that they seem to have difficulty stepping up to the plate on.

Click to expand...

Also, the EPA OMS can help with enforcing this. It is a US Federal Law that Maserati stand behind their products and protect our environment.

Thanks for all the tips guys. the light never came back during the last 2 days but i will get the car inspected soon and let you all know.