Help: 355 engine not running over 6.500 revs

The car: 355 2.7, SD1, 100 cell metal cats, Fuchs exhaust

The problem:
Since last week the engine refuses to rev over 6.500 - In all gears, even standing.
Performance under 6.500 revs is very good, all cylinder running properly.
Accelaration under load is pretty good as always before.
No issues there, just a smooth driver.
But then, around 6.500 revs, suddenly the fun it over. :-(
It's like a rev limiter going crazy way to early. :-(

It happend after routine service:
New belts + tension-bearings + checking the timings;
Washing the engine bay (first time since years ...)
New air condition fluid + dryer;

We did so far:
Checking the fuel system: New filter, checking the pump connectors, the pump itself, drained and looked into the empty tank, tried another type of fuel etc...
Anyway, the engine should get enough fuel from the pump.
From standing in idle, no gear, a little pressure on the throttle should be
sufficient to reach more then 6.500 revs with little fuel. But she won't rev.

We checked every electrical plug connector in the engine area;
Spark plugs are looking fine, compression is very equal on all cylinders.
No unusual smoke or other bad signs recognized.
Rev counter idicates plausible figures;
Mechanically everything seems to be all right.

Suspicious BOSCHs are: electrical sonde / ignition coil power modules

Next week I will check all possible systems on a Ferrari diagnose tester.

What do you think about this strange behaviour?
Thanks for every input and experiance!

cinque

 

That there is your problem.

I'm betting you have water in some of the connections. So what I suggest it that you pull EVERY SINGLE connector, blow it out with compressed air, maybe even put some WD40 on it first and then hit it with the air. Again you need to do EVERY connector, EVERYONE. If you want to find which one is causing the mis, you are going to have to run the car each and every time you dry a single connector. Extreamly time consuming. But if all you care about it getting the misfire gone, then do them all at the same time.

I would start with the connections on the Mass Air Flow Sensors, and go from there. But you are going to have to do EVERYTHING. Not only do you want to get the water out to get rid of the misfire, but you don't want it to stay and start things corroading. Then you'll really start to have problems.

So get some WD40, spray it in all the connectors, and then blow them out with compressed air.

Hope this helps.

 

thanks Ernie,

we did so twice. Now it's even worse:
There is a interruption of 12V power to the right ECU.
The right bank is dead, no spark, no fuel.

We swapped ECUs and cat vescovinis but the right bank is always dead.
Assume the parts o.k., cause they run properly for the left bank.
ECU fuse should be checked tomorrow and the related relais as well:
circuits energized by Ignition key BOSCH 0332 019 103

Maybe we can measure at the ECU wire-tree these days.
We just need to know where the 12 power supply pin is located.

Found a dokument about the BOSCH motronic 2.7, it's for a
Opel Vectra and a Fiat Punto :-/
But anyway, in this doku pin 18 is mentioned.
Pin 19 is for earth/mass.

cinque

 

Well if you are swaping the ecu's from one side to the other, and the ecu that didn't work on the right side now works on the left side, then I think your on the right track. You could have a problem with the wiring or connectors as you stated. One place you should look is between the firewall, where the wiring loom gets fed through the holes. If the rubber gromit that covers the metal hole is missing or worn, you could have a problem with the wires shorting out. The metal is pretty sharp and could cut into the wiring loom pretty easy. So try removing the ecu on the right side and then have a look inside to see what the condition of the wiring loom is where it goes through the firewall.

 

Does the car have coil wires? I'd check/replace them if it does.

 

Yeah that's a good idea. Swap the coil packs from one side to the other and see what that does. Also try unplugging the right side exhaust ecu and see if the right bank will run.

 

not bad guys!
Just forgot to mention that we tested with another coil pack from buddy's 355 car. And we also swapped the originals.
But there was no ignition possible.
As we swapped the ECUs we did it in package with the cat ECUs.

We will follow the wiring through the firewall. Good hint!
As you know, the ECU is distributing 12 V power to other parts,
especially the OT sensor. But it's without power - as expected.

Today I provided the motronic 2.7 PIN list to my mechanic, so he can do further research where the 12V interruption is located.

stay tuned!

cinque

 

Found a broken part:

Who is guilty?
A cable to the CAS = crank angle sensor (position).
We bypassed the rotten wire and the engine revs like cream now.

These wire parts are really too weak in design, especially for this hot environment.
I'm quite sure, the 355s are prone to fail this way.

Test drive will be tomorrow to check the + 6.500 revs.

Might be useful for the next 355 driver with a similar issue to check signals at pin 47 and 48:

47 CAS return: t2 cranking/running 0.25 max
48 CAS signal: t1

cranking: AC 4.0v+ (peak to peak)
idle: AC 8.0v+ (peak to peak)
cruise: AC 14.0v+ (peak to peak)

Mille Grazie for all your input & mental support so far!
Hopefully this italian electro-gremlin won't come back. (and no other error confusing the 355 engine)

cinque

 

Glad you found it.

 

A note on washing engines...a week or so after I bought my '81 Fiat X1/9 I washed the engine because it had gotten a little dusty. Engine would not start. Had to tow it home. Spent several days looking for the problem with no luck. Finally I checked the multi pin connector on the ECU which is located behind the passenger seat on the opposite side of the firewall from the engine. The water had migrated through the cable to the ECU connector! Blew it out good until dry, plugged it back in, and she fired right up.