Slow Down light and Glowing Cat

Experienced the famous "Slow Down" light, and as directed by my fine 550 Maranello, quickly pulled into a friends garage. Upon exit, observed a glowing hot Cat, opened the hood and observed to ensure nothing ignited from the heat. Unlike some who have experienced this light, it turns out mine worked as intended and saved me from a crispy Maranello!

I have ordered a replacement cat which I will install in due time, but my question to this fine panel of experts is:

what steps should I take to identify the cause?

Some important information to assist:

1) prior to recently purchasing, the car had a belt service performed.
2) after purchasing, I replaced a coolant return line (top of the block, towards the rear, under the intake manifold, wraps around to the reservoir).
a) this required removal of intake manifold
b) which also means fuel rails off as well
3) have driven several times for at least an aggregate of a couple hundred miles since this work, without issue
4) last couple of trips, have noticed a smell of fuel when starting up. Not sure if this is new or not, but only noticed it recently.
5) only right hand cat is toasted. And when I say toasted, the media burnt a hole in the cat.

I don't want to throw the cat on only to have it burn up again. I suspect there is excess fuel in the right bank of cylinders not burning fully in the engine. Suggestions?

Thanks in advance!

 

Check the spark plug wires, one may not be firing it's sparkplug or their may be some wires crossed to the wrong plugs

 

It is more likely that you have an ignition problem of some kind on that bank and instead of the fuel being ignited in the engine it is getting burned in the catalyst.
Did you not get a check engine light? Are there any fault codes stored in the motronic control unit for that bank?

 

I'd vote for the ignition issue as the most probable cause as well, however I wouldn't discount the possibility of a sticking injector. Do you know if your injectors have ever had a thorough cleaning?

IMHO, the ignition misfire detection in the Motronic 5.2 ECU's for the 550's is not reliable. For my first prototype COP system, the harness builder used soldered joints, and one failed, which resulted in a "hard" ignition misfire on several cylinders, and the Motronic didn't catch it, but kept injecting fuel into those cylinders that had no ignition.

 

Any wrench turners replaced these Cats before? I have removed all connections, but she is in there so tight, I either have to drop the exhaust manifolds or the muffller system rearward to get the space to separate the Cat from the first muffler bank. Curious what people have figured out here. I suspect rearward is less risky than the manifolds...

 

On my 456 we pulled the central muffler first; the cats came out easily then

 

That makes sense, looking at it. Thanks for the assist!

When I succeed, will post photos and notes for critique and improvement...

 

I have not found that. I once had a single intermitent leaky injector fingered by the motronic just fine. That was a day I really appreciated OBD2

 

Carl, I was referring to the Motronic's ignition misfire detection, not anything related to the injection.

By suggesting cleaning the injectors, I was simply giving the OP two avenues of troubleshooting, however if you've found that the Motronic catches sticky injectors, that's good to know! What sort of error code did you get?

 

John- No detection on my three leaking injectors even with the more sophisticated Motronic 7.1.1 compared to the 5.2 of your 550s.

 

Oh and 550

I just got standard p030x code for misfire right to one of the cylinders. I got Rc eng in torrance clean and balance all of them and voila.

 

Weird since the 711 in more sophisticated than 52

 

FBB- Who knows?

 

I believe you have to remove the rear mufflers first (after taking the rear plastic cover off), the the connecting pipes, then the center muffler/resonator and then the catalyzer. At least that is how I did it myself. The cats are tight to remove, but you will make it. Just make sure your tools are sll the way down the nut so you don't break them. THEN you have a real problem. Good luck.

 

Years ago, I had this in my TR. it was ignition wires and a distributor cap.

 

Guys,

Thanks a ton for pointers so far. I have succeeded in replacing the cat (separate writeup to follow for critiques and general knowledge; holy cow that was not what I expected!). Still have excess fuel getting to the cats. Ran ODBII and nothing shows. I suspect a right bank fuel injector may be slow to close or crappy, as that wouldn't have a code thrown and would still allow for the car to run, but would dump excess fuel into the system. Will clean those out and check wires/plugs (although if a misfire, those would have returned in the ODB II, right?). Any other common culprits you guys can think of?

Thanks,
Chris

 

Chris, there are other issues with the fuel systems on these cars that can cause injectors to stick open and/or not close fully. There are rubber cushions around the fuel pumps which are attacked by the ethanol in our fuel, then they disintegrate, and sometimes the particles find their way past the fuel filters and start clogging the injectors. Brian Crall has posted about this, as have others who have had symptoms similar to yours. Too, the ignition wires on these cars are now nearing 20 years old, and that's a LONG time for an HT plug wire, especially in the hellhole of a Ferrari engine bay.

If it were my car, I would not trust the OBD2 system to be highlighting ignition misfires, but would use more old fashioned methods of looking for them, and simultaneously, I'd be pulling down the fuel system and having a look for these disintegrating rubber particles that sooner or later are going to plague every 456 and 550 out there. You can get an indication if you have the problem by replacing your fuel filters, and then cutting the old ones open and inspecting for these black bits of rubber. Even if you don't find any of this rubber in your fuel system, I'd still send the injectors off for cleaning. It's just good periodic preventive maintenance practice.

 

Experienced the dreaded Slow Down light myself over a month ago. Cutting right to the chase, the cause was a bad/failed alternator.

I'd been having an intermittent alternator caution light come on, or it would stay on for an extended period after startup before going off. The day the Slow Down came on the alternator light came on and stayed on as I was driving home from a cars n' coffee, but I didn't make it all the way home before the SD light came on. All the electrics simultaneously had quit (no windows, no radio, etc, warning lights on dash lit up like a Xmas tree) and the ECU at that point had started to cut off the ignition to the left cylinder bank so car was hardly running. Pulled/coasted into a parking lot, got out/popped the bonnet, driver side cat was glowing. Subsequent diagnosis was that after the alternator failed and the battery drained down to the point where it could not provide sufficient juice to fire the coil packs, enough raw fuel got blown into the left cat to cause it to over temp.

So yup, a little excitement there, not to mention the expense of getting it repaired and back on the road. The passenger side cat was okay but the driver side cat was fried. No other damage, fortunately. Car is now back on the road again and runs perfectly.

Moral of the story: don't mess around with a bad (or suspected bad) alternator.

 

Ferraristas,

Just to close the loop, after fixing the cat, the fuel system, and several other things I found along the way, it turns out this was caused by faulty wires on the right bank. After rebuilding the wires per another FerrariChat thread, my baby is purring like new. The steps to get here weren't bad, as much of it was necessary maintenance, but wanted to share for the next person facing a Slow Down light (and I know, there are multiple culprits, but making sure this one is on the list).

One interesting thing is that the check engine light did not come on for this problem, although two error codes were visible on the OBDII. The OBDII for this vehicle is so incredibly proprietary it is frustrating. There was nothing specifying misfire as you would find in a Porsche or similar. Would love to have a good code list for this lady! Of course, that would be valuable for other ladies as well, I presume...

Will say, I love working on this car. She has some wonderful features to her. Amazing engineering for a 20 year old beast!

Cheers,
Chris

 

ColGraves

Good to hear you solved the SD issue. I haven't been able to solve mine yet after many years. Mine is also doing a flashing SD at cold start and also one side red hot. Replaced alternator, O2 sensor, check spark plugs ok, check wires are ok and with no luck of the dreaded SD disappearing. I was told that the car cat is not available. Would that be a problem?

 

Remove the injectors and inspect. Could be one or more injectors as the culprit.

 

LjT,

When you checked the wires, did you use an Ohmeter? Mine were looking serviceable from the outside, but once I had taken the wires out of the boots, I found several with a good amount of corrosion on them. I also found some insulation cracking in areas I just hadn't seen in the light of my garage. Rebuilding the wires proved far easier than removing the wires (damn throttle body in the way of cylinders 3 and 4!!!!). I also noted that to seat the boots, you have to apply some real positive pressure. There is a false seat sensation before the full click. It almost got me!

My fuel was a mess. When I changed my fuel filter, it had tons of black rubber in it. I changed out my injectors as a consequence, though that may have been excessive and incorrect. Alternatively, you can clean the injectors out. I have done this before using alligator clips, a 9V battery, and carb cleaner. It does work to get buildup out. With a Ferrari, however, I opted to just replace the injectors with new ones.

In all of my work, I found multiple little issues, such as an angular speed sensor on the bottom of the engine that had a good amount of insulation rubbed off (replaced that), and some connector boots in rough shape. Would love to know a good hack on replacing bad connector boots without redoing a wire harness!!! (anyone?).

Finally, I did hit the Mass Air Flow sensor with cleaner when I took it off to wiggle the throttle body back. Prophylactic, most certainly, but it was a "freebie".

As per OBDII codes, my first mistake was in getting a read initially. The Ferrari doesn't give you codes unless it is turning over. When I figured that out, a poorly seated sensor further didn't give me codes. Throughout, the CEL didn't light either, which was a big head scratcher. Once I had unscrewed myself with the OBDII sensor, I discovered two cryptic codes, with one being in the misfire area of the P-codes (though not specifically a misfire). That's when I decided to rebuild my wires, and joila!

Chris