New info on bank of cylinders shut down

88MONDIAL · #1 07-17-2012, 09:43 PM

I had a thread that I posted the other week about a bank of cylinders shutting down on me a couple of times. Well I just had my Nouvalari exhaust put on and tonight going to try it out. 80 degrees, 9pm great night. And now for the 4th time after 10min of the car being turned on, I loose a bank of cylinders, but this time I see a somewhat dim light in the upper right (in red) blinking. I think it said "slow down 1-4", i put the clutch in to make a tight turn and the car goes silent (dead)!! I cost into a parking lot, pop the hood, wait 5min and it restarts and runs great all the way home (about 6-7 miles). I have never seen this light before - on start up or when it's done this before, but I am 6' 1" tall and the steering wheel and my hand might have blocked it in the day light, at night I saw it flashing, but it was not a bright light either. I think on start up I mistaken my 2 center green lights for my slowdown lights. I just checked and those do say Check Engine 1-4 and 5-8. My slow down lights come on when I crank the key for literally for 1 second and go out right away which is why I've never seen them plus they are way up high where my steering wheel blocks my view!

What would a blinking slow down light 1-4 mean and why would it cut all power when I put the clutch in to downshift? Also, and I might just be paranoid at this point, but there seemed to have been a whine coming from the rear when I put the clutch in to slow down to my driveway that I never really heard before. I'm sure I'm just nervous is all.
Thanks for any ideas based on this new info.
Jim

**Future ferrari collector** · #2 07-18-2012, 02:11 AM

See my input right at the bottom of this thread, Stumble at higher RPMs

Slow down 1-4 happened to me but only at mid range revs. Car never died on me and was normal from idle to mid range.

88MONDIAL · #3 07-18-2012, 07:41 AM

thanks for the feedback, I should have noted that my car is a 94 348 Spider. Not sure if my problem is the same as yours was, plus you have a 355. Not sure if a crankshaft angle sensor could be the culprit, but it is REALLY hot in my engine bay after a 15mile drive. I saw it smoking when I parked in my garage with the sun setting behind my car twice. Normally I have never seen this. Just a light smoke coming from the manifold area I think, but who knows. It was radiating upward quickly and thinnly if that makes any sense. But like my friend with a 328gts says, his engine bay gets awfully hot too and can see stuff radiating off the engine when done driving under the right lighting conditions.

**ClydeM** · #4 07-18-2012, 07:56 AM

on my '95 355, the slowdown means the cats are too hot and if it happens enough, the ECU shuts down a bank & you go home in limp mode. It happened to me. And then, the temp would drop & the bank would kick back in until it got hot & then drop the bank again.

In my case, there were no cats, so too hot wasn't likely. I had an old style green temp sensor (black is newer) that was going bad. You can swap sensors & see if the problem shifts banks. If it does, buy a new sensor. If you read the ECU codes off the dash, you might also get a temp sensor error. I didn't do it so I'm not sure.

WHy it would kill the whole engine - I dont know.

bosshog8 · #5 07-18-2012, 10:27 AM

Quote:

Originally Posted by ClydeM

WHy it would kill the whole engine - I dont know.

I don't know either but mine did the same exact thing. Killed the entire engine, then started in a minute and ran fine. Finally got rid of these problems all together by removing the cat ecu's and never looked back. 1000 miles later and never had it happen again.

88MONDIAL · #6 07-18-2012, 10:47 AM

Quote:

Originally Posted by bosshog8

I don't know either but mine did the same exact thing. Killed the entire engine, then started in a minute and ran fine. Finally got rid of these problems all together by removing the cat ecu's and never looked back. 1000 miles later and never had it happen again.

So you just unplugged one end of the cat UCU going to the thermocouple (or would that work the same??). Are you running stock cats? I have stock cats.

alfa4711 · #7 07-18-2012, 11:14 AM

Jumped in this thread for curiosity as I owned a 348 TS years ago with the same problem.

Many times the problem is only a faulty relay, (like the one in the picture).
If I remember well it was located behind the seats, but i'm not so sure anymore (it was 20 years ago)

I changed it two times (there was no real problem but the defective relay giving a false alarm) and since I kept one spare in the trunk it did'nt happen again....

ciao

bosshog8 · #8 07-18-2012, 03:25 PM

Quote:

Originally Posted by 88MONDIAL

So you just unplugged one end of the cat UCU going to the thermocouple (or would that work the same??). Are you running stock cats? I have stock cats.

No, I unplugged the cat ecu from the main harness. Just unplugging the thermocouple will set a slow down 100% of the time. I run no cats, but in all honesty, every "normal" car on earth has no cat thermocouples in it and if the cat goes bad it runs like crap.

Granted if you are running the thing flat out for a while then this system could come in handy in the event of a cat failure but thats not my thing so even if I had cats I would have removed the ecu.

**tcannon** · #9 07-18-2012, 06:00 PM

When one bank is shut down, the engine will not idle on it's own. So unless you are giving it some throttle when sitting still with the clutch in, it will die. At least this is how my 348 performed when I had one bank shut down.

88MONDIAL · #10 07-18-2012, 09:31 PM

Sorry, I'm unclear as to what to unplug. If I unplug the cat ecu from the thermocouple, then I also need to do the second plug going to the main computer as well. so both plugs need to be unplugged in order for it not to get a slow down light anymore? If I'm hearing you right I just need to unplug both of the connections from the cat ecus.

**ernie** · #11 07-19-2012, 12:45 AM

Just unplug the main connector going to the wiring loom/s for the Motronic ecu/s. With the cat ecu's unplugged the engine with still run, but you will get a silent code (meaning no check engine light, but the Motronic will store the 4121 code referring to the cat ecu's).

88MONDIAL · #12 07-19-2012, 07:44 AM

Quote:

Originally Posted by ernie

Just unplug the main connector going to the wiring loom/s for the Motronic ecu/s. With the cat ecu's unplugged the engine with still run, but you will get a silent code (meaning no check engine light, but the Motronic will store the 4121 code referring to the cat ecu's).

I'm an idiot. I have no idea where that is. I only know the two plugs that come off each of the cat ecus. The cat ecu is a flat box thingy and it has 2 cords coming out of it with connections. Those are the only ones I know. Can I undo one or both of those? Is the one NOT going to the thermocoupler what you're referring to? Sorry, I've learned a lot about what and where the cat ecu is/does and the thermocouplers, but other than that, I'm back in the dark. I do feel good about what I've learned so far and can say I feel more comfortable just knowing that little bit of info. Thanks guys!

**ernie** · #13 07-19-2012, 01:05 PM

Follow the thermocouple wire from the cat to the cat "ecu". Once at the cat ecu unplug the connector at the cat ecu that goes to the wiring loom. You do NOT need to unplug the thermocouple. Leave the thermocouple plugged into the cat ecu. ONLY unplug the cat ecu from the wiring loom going to the Motronic.

Capiche????

DaveK · #14 07-19-2012, 01:14 PM

Quote:

Originally Posted by 88MONDIAL

Is the one NOT going to the thermocoupler what you're referring to?

Exactly. Unplug the one NOT going to the thermocouple.

88MONDIAL · #15 07-19-2012, 02:44 PM

Excellent, thank you!