348 slow 1/4 light coming on, please help!!!

First thing you should try is swapping the warning light ECUs and see if the bad behavior moves to the other bank or not -- just follow the shielded wire from the thermocouples to the warning light ECUs (usually they show this system in an OM illustration, but maybe not on 348).

With regard to the shifting, many good threads on tweaking up/checking the complex 348 shifter arrangement (but I don't recall any specific keywords that would be any better than "348 shifter" for searching -- so I leave that homework for you).

PS Although it doesn't matter much here, please give year and version too -- i.e., putting year/model/version in your Profile would be a courtesy IMO.

PPS Why does everyone's first post always have to be "I'm having a horrible problem" -- welcome to FChat

 

I have heard from a mechanic that sometimes people put new Catalytic converters in when they change the exhaust. Sometimes a mechanic will strap the ECU connectors to the frame of the car instead iof installing them in the new catalytic converters. This is supposed to avoid getting the slow down 1/4 or 5/8 lights. However, sometimes a lack of information from the ECU causes the computer to turn on the slow down lights. I was also told that the slow down lights are common on every 348 and the replacement ECU's have an epoxy covering over the connector to prevent corrosion that is typically why the older ones short out and cause the malfunction in the first place.
BT

 

lee -- please see this thread:

http://ferrarichat.com/forum/showthread.php?t=16859&highlight=348+ECU

in post #6 there's a jpeg showing the 348 exhaust system. Item 16 in the jpeg is the thermocouple and the small rectangular box that it plugs into is the slowdown warning light ECU (unfortunately, the item numbers are cut-off on the bottom of the jpeg). Each bank has a thermocouple mounted in the cat exhaust exit area and a warning light ECU that are completely independent systems. You can swap the warning light ECUs and/or thermocouples around to deduce who is the bad player (if you're getting an obvious electrical gremlin like the slowdown warning light just staying on at cold-start up).

Is your self-test working well every time?

You could also try searching here on "348 ECU". Although not every thread will be on point, you'll get many good ones for understanding how your 348 works.

 

No, they are two different devices -- the O2 (Lambda) sensor is mounted in the cat inlet side; the thermocouple is mounted in the other (exit) side of cat.

In that jpeg, item 36 is the Lambda sensor.

 

cat sensor mate, probably just sensor thats faulty, get it replaced or get a garage to replace it

 

Unplugging them will turn the light off, but beware of cat overheating. Are you experiencing power loss also? You should be.

The bad cold shifting you'll probably just have to live with especially if it goes away after warm up. Not much to adjust there
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91 tr is correct, try swapping the ecu's , slow down lights should change as well from 1/4 to 5/8 or vise versa. the part will probably run you about 400 bucks maybe a little less, here is a pic of what it looks like, real simple to remove and replace. by swapping the ecu, this will determin if the ecu is bad [ if the slow down light moves ]
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Lee,

Did I read you are running a single plate clutch on a '91 ?

If so I am surprised as I have a late '91 with dual plate and I understand the conversion is expensive

I believe the gearboxes are pretty bullet proof so would be surprised if you have a terminal problem

Cable adjustment to the gearbox may need attention. Suggest you have a specialist check it over although there are threads on here discussing the topic.

Check engine lights come and go.

1st operation is always clean the connectors and take it from there.

Good Luck - once over these initial issues they are fantatstic cars to drive.

John

 

Id bet its the Thermalcouple ECU. If they are anything like the ones on the 355 they are crap. They are prone to hairline cracks and if a bit of moisture gets in they are junk. The other thing may be an 02 sensor not grounding.