F355 Cylinders 5-8 cutting out

Swap the 1-4 and 5-8 warning light ECUs -- if the "problem" moves to the 5-8 bank you know that that warning light ECU is faulty.

Is your self-test working well/always when you turn the key "on"?

Did you know there was a self-test?

PS If you have no cats in place, yet the warning light comes "on" (when it's not doing the self-test), this is near-conclusive that the warning light ECU is "bad". If no cats are in place, you can just unplug the faulty warning light ECU to restore the operation of that bank (if it's the warning light ecu causing the trouble) -- but I'd only do that as an emergency fix, not a long-term fix -- if the warning light ECU needs replacing, the longer you wait the more rare/expensive it will become -- JMO).

PPS Did you really read this thread?

 

Steve, just read your answer to my post...2 months late .

Are you sure? I thought that that tesatrossa's ALSO cut out if it was overheating?

The owners amnual states that it blinks at a slight overheat, then goes to a solid light at a certain temp and "buzzes." I could swear it said somewhere that the bank is then shut off...

My car does none of this...the light just goes ON, no buzzing, no blinking, no nothin'. The goes out. I keep intending to change the ecu's from one bank to another, but haven't had a chance. The light goes on extremely infrequently...

 

Very sure -- on a TR, there are no electrical connections from the warning light ecus to anything other than the bulbs in the dash (i.e., no electrical connections to the injection ecus).

Sometimes the translations aren't the greatest/clearest, but glad to discuss any "evidence" that you can present.

I'd bet that on 99.99% of TR that that buzzer has been disconnected/disabled -- my TR came to me that way and it's not something that I'm going to fix .

Doing the swap will confirm/deny if you've got a Gremlin in one of your warning light ecus, but how is your self-test working? The warning light that stays "on" at the wrong times gets noticed, but a warning light that doesn't come "on" (every time) for the self-test is also a bad sign for the ecu (but people tend not to notice/care because it's not as annoying as a light and a buzzer ).

 

I have a 348 and had intermitant slow down light 1-4 and a rough idle intermitantly.

The light would come on solid (not blink first) then shut the bank down shortly
after that. you can look back at my posts asking for advice.
swapped ECUs side to side and for the heck of it checked the FPR on that bank because I'd already replaced the one on bank 5-8 that was leaking causing hard starts when hot. Replacing the one on 5-8 corrected the hard start problem but
evidently the one on bank 1-4 was allowing enough raw fuel into the air intake
plenum on that side to cause the rough idle and slow down issues because I haven't had
either problem since a month or two.
Boy you'd be impressed how well these 348s work when they're right )

Oh, when the bank got over fueled it smoked white a lot at times on warm up.

 

Thanks - The self test is always fine - well I assume so both lights come on then go out after a few seconds of the ignition on- I then start the car - should have said but was rushing when I wrote the post that I've done the ECU swap and it made no difference - would a coil pack have the same effect ?

 

Are you saying that with testpipes in place (i.e., without cats), you are having the 1-4 overtemp warning light go "on" occasionally regardless of which warning light ECU is used on the 1-4 bank? (Without cats I don't see how this could be a true overtemp indication).

 

That's exactly right - I am not bothered about the occasional light as the cats are out of the scenario - the probelm is the shut down of 1-4 bank could it be both cats ecu's are faulty from the light perspective - and that I have something else causing this....I was hoping a coil pack but my experience of them is that they either work or they don't maybe its time to check the main ecu what do you think ?

 

Which ecus did you swap (from the pictures below)?
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(Since both of those ECUs "work OK" on the 5-8 side) It would have to be some sort of electrical Gremlin/crosstalk/wiring harness short/etc. -- the coil pack (or anything else in either the ignition or injection systems) can't be the problem because without cats there is nothing to ignite any excess fuel (if present) in the exhaust stream.

Unfortunately, you've got a "new" one

 

Just for confirmation - I swapped the small units and not the main Bosch Engine Management Unit.

I have been following these threads on and off for quite a while. I used to have a starting 'problem' which would only manifest itself when hot and left for say 5 to 10 minutes needing a good old churn on the starter to fire it up. This was resolved when the test pipes were fitted so I was quite hopeful that I'd resolved the limp mode thing.

What I will do is change both of the cat ecu's for new units and see what happens. I will let you know.

 

I found aftermarket plug wire kit here, you make your own kit, with wires, + plugs caps.., The ref K is ok,you only need to cut it shorter.I will make some photos.
The price is good, about 120 Euros.
http://www.comptoir-hydraulique-automobile.com/autolec_014.htm
nico

 

Again again same problem of cylinder lost under 3000rpm, all the plug wires are new, all connectores are cleande same for flywheel sensor,not warning light on dashboard but still run bad !
Should I burn this crazy car ? I dont know what to do anymore.....

 

I tested a 348 coil on my 355 to try to find the cutting cylinders problem and it was not better...maybe worth...I thought it was not same...
I changed too the the power module (same like 348) and it did not change the problem...
When I unplug the coil for 4 cylinders I feel that the 1.2.3.4 cylinders have better sound that the 5.6.7.8 so I think it is a coil or spark or sensor for this cylinders that is damaged...plugs have done 12000km only.
Any idear ?
can a thermocouple be out of order without light on dash boad ?

 

I saped the thermo couples unit, did not realy found better but found this little damage on one on the side I think turn bad.
would you change it ?
will try to post pics.
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That is EXACTLY the problem with those units. The potting compound separates from the plastic case and allows moisture to get in.

Changing for a new one (€400 !!!) cured my 348 cutting out 4 cylinders (except for VERY occasionally, and the dealer thinks that's because the other unit also has this fissure)

 

ok thanks for reply ! did you have a warning light on dash board ?

 

Sometimes the warning light just flickers gently. Sometimes the 4 cylinders cut out without any warning light. To reset whilst driving, I just drop the clutch, then the engine dies, then I let the clutch come, the engine restarts and all 8 are working.

 

me I have to drive more than 3000 rpm and it is ok.
A thermocouple failure does troubles only at low revs or at high revs too ?
because my 355 2.7 is perfect after 3000rpm...strange !

 

I post a little sound clip of my 355 having troubles
please listen to it to have a better idear of the cause
View attachment 355lacata.mp3

 

I reasently had a problem with my 348 cutting out a cylinder bank.
Sometimes it would flash the slow-down light, sometimes it would stay on full
sometimes it would just shut the bank down and no light.

I asked around and was told that the green potted units don't normally fail but
I had one black one and one green one. the black ecu I had looked just like that
splits on the sides where the potting material separated from the plastic.
How I found the problem was moving them from side to side, the symtoms moved along with the black ecu.

A new one, with green potting material was bought from Ricambi America.
that solved my problem....

 

it is agood solution moving them from side to side, but I can not identify at 100% the side that run bad...that is the reason why Im not shure of it.

 

I've got a spare 348 exhaust ecu. PM me your address and I'll mail it to you for a test.

However, your exhaust ecu's don't *cause* bad running conditions (e.g. stutter, pops, hesitation, etc.). They can shut down a bank of 4 cylinders, but a properly-running Ferrari engine will idle smoothely even on just 4 cylinders.

So you have a problem outside of, or in addition to, a potentially bad exhaust ecu.

 

don't consider me an expert by any means, but my 348 wouldn't even run on idle on 4 cylinders. Your sound clip sounds a bit like plug leads crossed, bad spark plug, valve burnt (eeekk!!) or anything like that rather than a systematic shutting down of 4 cylinders..

To be honest, when running on 4 cylinders the 348 runs fairly smooth - not lumpy like on your sound clip.

 

the 348 ecu and 355 are not same I think !
what dop you think of a flywheel sensor running bad ?

 

That would cause a poor running condition. Same thing if the wiring connections to a flywheel sensor were bad.