328 slow down light ....again sorry?

SLowdown light usually means overheated Cat usually caused by unburned fuel getting into the Cat which in turn is normally caused by an ignition problem to one or more cylinders or a whole bank.

Therefore if the car feels like its running right & there is no major stink of unburned fuel then I'd be more inclined to think its just a bad sensor.

I.

 

My 328 (1986 model) suffers fromt he same syndrome. Just a flickering in my case, though. Like you, I feel no loss of engine functions and certainly no cat glowing. My mechanic told me that it would cost about $2,000 US, to replace a faulty sensor, since they don't make exact replacements, and he would have to take a newer sensor and modify it.

I never redline my car, and wehre I live the temperatures are rather moderate, and still it comes on occasionally. Kinda takes the fun out of driving my car, so I am going to have my mechanic replace the sensor.

 

If you have run the engine its unlikely anything is still any damp in there so hold the WD40 (!)

I don't believe the ECU is smart enough to put the car into any sort of "limp mode" or shut it down on you

Suggest you go and speak to your technician & get them to check it out for you & give you a price to fix it.

I.

(who's UK spec 328 has no cats, related sensors or nasty "slow down" lights )

 

A friend of mine with a 328 had the same exact issue. He took it to a dealer, who immediately rec'd a new cat. Given the ridiculous price the dealer would charge for this, he took it to an independent Ferrari mechanic who removed the cat and found absolutely nothing wrong with it. Since the car ran perfectly and light came on or flickered at all temps, including before even warming up, it was determined to be a malfunction somewhere in the light/sensoring system. I've lost touch with this guy, but as of last contact, he was unable to locate the problem as yet and the car continued to run perfectly.

 

I used to have a Mondial 3.2 and now have a mondial T. Anyway I had a bad ECU for the slowdown light. I did a lot of reseach into it. It basically just turns on the light and sends a signal to the ECU. I have built an engine monitor that is about the same size for aviation use that could do the same thing. My device monitors EGT (using the same thermocouple that Ferrari uses), cyclinder head temp, rpm, etc. I could easily make a couple of changes in it to replace this Ferrari ecu. I could even add a display to it to give you absolute temp of each cat rather than just a threshold to turn the light on.
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Yesterday afternoon, while on a short drive, the slow down red light came on. After a five minute or so interval it went off, then it came on again and stayed on, then off again. Sometimes a bump on the road would bring it back on, it would then flicker and go off again. Since I've removed the catalytic converter, it did not concern me very much, though I found it annoying. While the light was on one of the times, just for grins, I put my foot into it and it continued to behave no differently--on then off. By the time I headed home, the light had stayed off over half an hour. I checked under the hood, under the car and found nothing unusual, same smells, same amount of heat (very little) as always, no evidence of anything amiss. I'm guessing, but next time I go out, there'll be no slow down red light or else it'll behave pretty much the same as it did yesterday. Glad I have a test pipe, a red light on the dash would make me think I needed a new $2K cat from Ferrari.

 

Now, if you can make a full, DIY'er ODB and/or reader for the T, well, me thinks we have at least one buyer here

 

Guys,

From what I learned when the slow down light is on the ecu runs only in open loop mode. So you will not notice a performance difference since it is running on your learned parameters anyway (until you disconnect the battery). It is basically letting you know that you could be overheating and damaging your cats.

I think an absolute EGT guage would make more sense for knowing how your engine is operating. However the cat is way too far back in the exhaust to know mixture and how far off peak horsepower you are. The only thing you can really learn by measuring temp in the cat is what is the cat temp and if you are overly rich or lean on that side.

The ultimate would actually be a thermocouple about 2-4" from the pistons in each of the headers pipes to know if your performance and mixture is at peak. This would let you know cyclinder to cylinder differences (i.e. know if one plug and which one was missing, know if you had an injector problem, or even unbalanced flow potentially. ) It would also let you adjust your mixture for peak HP, peak economy (not for Ferrari drivers), or a specific EGT. This is what this device does for airplanes. Obviously mixture control on a Ferrari is controlled by the ECU and not the driver/mechanic like airplanes.

Anyway I know these "SLOW DOWN" ECU are getting hard to find and expensive. I just wanted to let you guys know there is another option. I can build you one. Probably about $300 or so. You tell me the temp you want to turn it on. I can verify the temp.

 

I've tried to reply to this thread several times, and just keep getting lost in my thoughts and concerns.

I really can't stress how important it is to have this system working properly on the car. Even if you are running test pipe(s), the information provided by the slow down light should it come on can save your engine. An over rich condition will ultimately cost you a set of pistons, rings and liners. If the cat(s) are still on the car, then the stakes are much higher. A red hot cat is a fire waiting to happen.

 

With the cat removed, what was done with the thermocouple that is normally screwed into the cat?

 

Both the thermocouple and the oxygen sensor were screwed into the test pipe--it has the correct fittings/bosses for the two, in the same locations as the original converter.
Having the pipe for me was the best external engine modification possible: a) reduced engine under hood temperature, b) weight savings of around 15 lbs, c) slightly deeper exhaust sound, d) better throttle response. All for around $300 if I remember correctly. The only disadvantage is r/r every two years for emissions testing here in Colorado. All in all well worth it since it only takes a couple of hours and fresh gaskets.