348 keeps dropping a bank

[NeilH]

Ok - some suggestions required please. My 348 has been playing up a while now, but is getting worse and finally embarrassed me on Sunday morning on route to a show ...

One bank occasionally does not fire when the car is started, mostly from cold but has done it from hot too. Not every single time however. Normally if it decides to play up and the car is cold - i.e. start of the day, the routine goes something like this - car starts on one bank (because it is cold it starts ok on one bank) - once running, either leave for 10 to 20 seconds or hold the revs at about 1500rpm and the 2nd bank comes in and all is good. Once running, she normally behaves for the rest of the day. I get no error lights AT ALL during this process. It is always the same bank. I have changed the Coil pack, the CAT ECU and checked all the wiring and connections in and around that area.

On Sunday I lost a bank while driving, again no warning lights of any kind - it has done this a couple of time before but a very long time ago. Dipping the clutch - shut off the ignition, back on again, wait for lights to go out and lift the clutch and fire the engine back up has sorted it on these rare occasions ... however, not this time and I had to pull over.

Long story short, having put a call into the AA for a rescue and threatened to sell her - I finally got it started again on one bank and after about 1 minute, perhaps a bit longer, the 2nd bank fired up.. Not wanting to risk the old girl throwing another tantrum further away from home, I drove home - took about 15 mins on fast empty roads, without issue or missing another beat - Threw a cover over her and took something else out to play instead.

So - Obviously I need to get to the bottom of this and I am thinking Crank Sensor

Anyone else care to suggest somewhere else to look ? She had a lot of work done earlier in the year inc a full service and typically the garage said it never missed a beat or played up the whole time they had it and drove it

[348jeff]

If its always the same side that would help with diagnosis as you can swap parts between sides and check if the fault folllows the part (and wont cost anything but time to do).

Little check list for you....

1) Coils (which you've already done).

2) Ignition modules (next to the coils)

3) Check wiring on crank sensors and that they are clean/swap them round as per initial note.

4) Spark plugs - check condition

5) Relays in the footwell for fuel pump and ignition - about £6 each so would just replace with new

6) HT leads

7) Clean your MAFs with MAF cleaner and any electrical contacts with contact cleaner

[NeilH]

Thanks for the reply.. Yep always the same left hand bank.

1) Done
2) Done (well swapped side to side)
3) - This was my next port of call
4) Recently renewed
5) Ah - now this was not on my radar but good point. I have not been over come with the smell of fuel when this has happened come to think of it, suggesting fuel might not be being pumped into that side when the problem occurs and I have had silly fuse connection issues.
6) Checked and visually look ok but will put on the list
7) - OK - MAFs ???? Sure once you tell me it will be obvious but right now - not a clue !

[348jeff]

Cleaning crank sensors

http://www.clubscuderia.co.uk/forum/showthread.php...

Cleaning MAFS

http://www.clubscuderia.co.uk/forum/showthread.php...


Passenger well relays

http://www.clubscuderia.co.uk/forum/showthread.php...

http://www.clubscuderia.co.uk/forum/showthread.php...


As a minimum I would replace relays C & D (cylinders 5-8) and ,L & N (cylinders 1-4)which are the fule pumps and the injectors - in fact do these first! :-)

[otta]

had the very same issue on my 355, after lots of frustration and 2 trips to a specialist I decided to tackle the issue by (i) identifying offending bank and (ii) switch over anything possible from one side to the other.

It was the relays in the passenger foot compartment. Very cheap fix for an annoying problem...

[Cerbieherts]

It's also worth removing and cleaning the earth points on the valve cover, as these also give the same problem. There are two per bank.

[NeilH]

Right .. Crank Senors changed ... problem still exists...

Ran out of time to strip all the relays and fuses from the footwell and clean / replace so that is my next task.

Thanks for the other suggestions .. all being added to the list

[Behemoth]

otta said:

had the very same issue on my 355, after lots of frustration and 2 trips to a specialist I decided to tackle the issue by (i) identifying offending bank and (ii) switch over anything possible from one side to the other.

It was the relays in the passenger foot compartment. Very cheap fix for an annoying problem...

Doesn't sound like that one "specialised" much in 355s Anything electrical that feeds the banks separately have to be prime suspects and I'd go from easiest check to hardest. Relays seem like the easiest on the list.

[otta]

Behemoth said:

otta said:

had the very same issue on my 355, after lots of frustration and 2 trips to a specialist I decided to tackle the issue by (i) identifying offending bank and (ii) switch over anything possible from one side to the other.

It was the relays in the passenger foot compartment. Very cheap fix for an annoying problem...

Doesn't sound like that one "specialised" much in 355s Anything electrical that feeds the banks separately have to be prime suspects and I'd go from easiest check to hardest. Relays seem like the easiest on the list.

Well unfortunately I had to do it myself after opening up the owners manual. The car decided not to give any troubles while at the specialist.

Either ways for the OP what I suggest instead of blindly replacing electrical pieces to identify first which bank is causing problems (can do so by unwiring spark module on one bank when the car is running on one bank only or by (very carefully) checking manifold temperature with your hand) and then swap electrical pieces/sensors until problem switches as well. Then you have the culprit and can change it.

The two banks work as separate engines so easy and cheap to identify offenders.

[NeilH]

Hello OTTA .. Thanks for the post.

I know exactly which bank is at fault and have been working through various steps in a logical manner on that bank. So far I have replaced with brand new items the Ignition Module, the Crank Sensor and the Ignition coil on the bank in question. All of the relays and fuses in the footwell need to be pulled and cleaned / replaced - the car was allowed to get very damp prior to my ownership so I have experienced some odd electrical issues - I will be logical about it I can assure you !

Once I have gone through the fuses and relays, if the problem still exists, I will turn my attention to the MAF for that bank.

[otta]

NeilH said:

Hello OTTA .. Thanks for the post.

I know exactly which bank is at fault and have been working through various steps in a logical manner on that bank. So far I have replaced with brand new items the Ignition Module, the Crank Sensor and the Ignition coil on the bank in question. All of the relays and fuses in the footwell need to be pulled and cleaned / replaced - the car was allowed to get very damp prior to my ownership so I have experienced some odd electrical issues - I will be logical about it I can assure you !

Once I have gone through the fuses and relays, if the problem still exists, I will turn my attention to the MAF for that bank.

Usually the MAF should come clean post 2k rpm even if electrically it is faulty. If it is termo or o2 or cat you would get a light usually. Other than that is fuel or electric. Not sure if cleaning the relays is enough and not clear if they have gone from the outside. But swap and check if the problem does!

Good luck in finding the problem

[NeilH]

Found the problem !!

While going through all the fuses and relays last night in the passenger footwell, I discovered someone had modified a connection behind the fuse box, I assume for a previous alarm, and had broken into the wiring for the ECU for Cylinders 5-8. Although the additional wiring had been removed, the original wire had been damaged and by moving the wire slightly with the car running, the bank would cut in and out exactly as it has been on the road. The fuse panel was not properly secured and so was able to move around - hence the wire allowed to move.

An easy fix to cut away the damaged wire and make good.

Thanks for all the suggestions and pointing me in the right direction regards the electricals in the footwell.

[Behemoth]

Great that you've sorted it. After market alarms caused electrical gremlins on every car I've found them in. I hope there's no trouble elsewhere. For Thatcham paperwork iirc the cuts into the loom have to be in more than one place and they installed red herrings pretending to be the alarm wires but doing nothing ... until the contacts corrode. Nightmare.