F355 Cylinders 5-8 cutting out

the connector of the ECu for the left cylinders (passenger side) was bad connected and caused trouble ! just found and ,now everything is ok ! very happy !

 

Niclolas, great news! Thanks for the follow up post.

 

I have again exactly the same problem ! I drove 400 km under the rain very important and now it run bad...whater into a wire plug ?
will check again...

 

This exact thing happened to my friend on the way home from a trackday yesterday, does anyone have any pics of these sensors so we can remove them and get the car useable again

 

http://www.ricambiamerica.com/product_info.php?cPath=2_735&products_id=208023

 

Thanks Dan

 

One thing I forgot mention was it was very heavy rain, I wondered if that might play up a sensor

 

jackpot!

 

I had too, a lot of rain before it started runing bad...wherethis csensor unit is located ?
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This site is awsome and helps us in many ways without having to go to the dealer and getting raped. Thanks to all.

My problem is that my slow down 1-4 comes on and cuts those cylinders out for a short time. I dont drive it in the rain. I have no cats. By the way straight pipes and a tubi make the 355 a much better ride. Anyway I swapped the o2 sensors and the light still comes on and off sometimes cutting the 1-4 cylinders and sometimes not. All depends on how long the light stays on. I have now swapped the temp sensors and still the same thing. I guess I will now try to swap the ECU and I will take a picture for our french friend and any future readers. I hope this works because if it doesnt I dont know where to look next. Thanks to all and if you think of anything els please let me know. " I doubt the spark plug wires would cause the slow down to come on would it?

 

The slow down light is *only* controlled by the cat ECU and has nothing to do with the O2 sensor as a triggering mechanism. What you can do versus what should be done are two different things. I'll let somebody who doesn't have the word "Sponsor" attached to their name disclose the answer.

 

Thermo couplers or ECU

 

The cat temp ecu's. I will interchange those and see what happens. Any other ideas are welcome. "Jack Russell" Tell me whats on your mind please.

 

Since you have no ignition source (hot working cats) for unburnt fuel (if present), it is virtually impossible that you're getting a true high temperature indication (i.e., the warning light ECU for that bank must be wacky, but do the swap to confirm).

Since you have no cats, you are not at any risk of igniting the nearby coachwork or engine components (when/if unburnt fuel is present in the exhaust stream) so I think that you could try just unplugging the bad warning light ECU if you wanted too, but this has a long-term downside IMO. If I was buying a 355 that was originally equipped with this system, and the self-test of this sytem didn't work right (even if it didn't have cats), I'd deduct the $ cost to repair from the price I'd be willing to pay -- and the cost to replace these ECUs is probably only going to go up in the future. They may even become unavailable so you risk trying to sell a car that can't easily be put back to stock which limits the selling market -- JMO.

 

for me everything is ok now, since the car is "dry" (no more whater) it was certainly due to whater in a plug or on a sensor....
thanks
nico

 

Yes but unplugging the bad warning light I dont think will stop the 1-4 bank from shutting down.

 

Just as a datapoint:

My ecu on a testarossa also occasionally just lights up. It never goes through a blinking phase, and it seems random. Sometimes on for seconds, sometimes for minutes. I have never had it cut out the ignition.

I would think that if the ecu were at fault, you would have a similar scenario. But you are actually loosing spark. Does this agrue against the ecu being bad?

 

When the slow down 1-4 light comes on it is doing its job by cutting the spark to that bank. My problem is finding out why the light is coming on.

 

Finished swapping the cat. temp. ECUs around and it took 20 minutes tops. Took it out for a ride and low and behold the 5-8 light flashed on for about 3 sec. All I need to do now is purchase a new one and replace it, problem solved. Now wheres the best place to buy one other than the dealer? Thanks all

 

1/4 or 5/8 slow down lights,the problem is caused by the thermo couplers or as techs call them cat temp ecu's change those and the problem should go away.also you should change them all out due to if the the problem occured on one side it will happen on the other side.
the heat in engine compartment deteriorates them and that happens very often

 

Technically , this is correct -- if you just unplugged the warning light bulb only, the warning light ECU would still send the signal to the corresponding injection system telling it to shut down. However, when you unplug the warning light ECU, not only do you unplug the bulb, you also break the connection from the warning light ECU to the injection system -- have you tried it?

 

TR are not as sophisticated as the later models -- the warning light system on a TR is completely independent of the injection system so it never shuts a bank down intentionally. Because people would never actually stop when the warning lights came "on" (I present yourself as more evidence of that ), whether it was a true or false indication, the manufacturers were essentially forced to add the automatic shutoff on later models.

 

Thats nice to know especially if your in a bad spot. I did swap the left and right ecu this evening and the problem has moved to the other side thus telling me that the ecu need replacing. Thanks 91tr

 

I want to clear up some confusion here.

The thermocouples and the cat temp ecu's are not the same thing.

The thermocouples get screwed directly into the catalytic converters, and are what directly measure the temperature of the cat.

The catalytic converter temperature electronic control units (cat ecu's) are what receive the temperature reading from the thermocouples and then send that temperature to the engine management system.

You can have a properly working thermocouple and have a faulty cat ecu, or vice versa. The reason you swap the cat ecu's from one side to the other to test is just that. If by swapping the ecu's from one side to the other you get the light to change side, as was the case here, then you have ruled out it being an isssue with the thermocouple, and it being a bad ecu. Also if after the cat ecu's were switched and then the light were to appear again on the same side, then you would have ruled out the ecu as the problem, and then have narrowed the problem down to either a bad thermocouple or the cat actually getting hot. You would have have done the swap side thing with the theromcouples, again to see if the light moved. Then if both were ruled out then you have a problem with the fuel being too rich, which then sends you to a whole different run of tests.

So don't confuse cat ecu's and thermocouples as one and the same.

 

Hi,

My 348 suffers from an intermittent fault - sometime the 1-4 light comes on and sometimes it doesn't but 1-4 bank certainly goes into limp mode.

I've read all the threads and tried the following -

1. suspect faulty thermocouple - replaced with new - no difference

2. faulty cats - remove and replace with straight through TUBI pipes - great sound but no difference

Although intermittent the shut down seems to come on when the engine fans cut in - I don't always get the dash lights though and again this isn't always the case.

Occasionally - but not always - switching off and restarting sorts the problem
but this may just be coincidence.

I've tried all the connectors etc when it's running in limp mode but that doesn't make a difference.

Any ideas ?