456 Manual (new owner questions) - advice please

Stumble starting is common but not stalling. I would check fuel pressure. If fuel pressure is fine then ignition. If ignition ok then injectors.

No experience with CEL but your cas has independent banks for fuel and ignition. You can swap the modules. If the problem follows the modules the. You have your answer. They are just in front of the doors under the hood.

 

when was the last oil change and who did it?

 

Fuel line check valves. They go bad, cause intermittent CELs and rough starting. To get to all of them requires removing the tank.
I had the same thing on my 95

 

You need to read the cel code on that bank. There are instructions in the service manual. You hold down a switch near the ECU and the CEL flashes the code. I am chasing a very similar problem on mine and would be interested to know what codes you get.

 

OBD I codes can be read out without the need of a special tool - there is a button behind the vertical footwell liner on each side which if pressed in the proper sequence will allow you to readout the stored codes as flash sequences of the CEL light. How to do this as well as how to interpret the flashes is explained in the shop manual which I believe is now available on line.

The modules just in front of the doors under the hood are wired to thermocouples in the catalytic converters and will result in a "slow down" light if excessive temperature is sensed not a check engine light.

I looked at the parts manual and can find no check valves in the fuel line although there are various valves as part of the antievaporation system. I can't see how these would cause the above problems but perhaps - "cls" clarify what parts he is referring to and how they relate to the problem.

I have a 95 465GT with the same problem which appears to be a common one usually including a rough or no start on the first try and a normal start on the second. CEL is usually a "lambda regulation problem". I did lots of testing including electronic ignition analysis , fuel pump capacity and pressure testing, O2 sensor swap. and MAF sensor cleaning / swap and TPS adjustment. In the process the problem which was always intermittent disappeared - frustratingly not obviously tied to anything I did.

DOES ANYONE HAVE A GOOD EXPLAINATION / SOLUTION TO WHAT APPEARS TO BE A COMMON PROBLEM FOR THIS MODEL?

 

That is the same thing with mine - lambda regulation problem. I have done most of the things you mention, but my next step is to change the coolant temp sensors under the intake manifold. Also, I recently discovered what appears to be fuel seeping from the fuel rail to one of the injectors, which may also be the problem so I am looking into that. If I figure out the problem, which is a big IF, I will post what it was. Thanks.

 

I couldn't find the procedure in the 456 manual but it is in the 355 manual. I'm assuming your car has Motronic 2.7


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Sorry, there are only two parts to the procedure. I posted parts of it twice. Hope it helps. The button for the right ECU is in the passenger foot well, just ahead of the door. You pull of the vertical panel and you should see the button near the top.

 

the reason i ask is that changing the oil, actually adding oil, to the 456 is a tricky thing.
first off, you dont always get the full 11 liters out, more like 10.2 to 10.7 liters.
the tank into which you dump the oil, is shaped like a stepped pyramid, with the result that if you are not careful, or you dont know about this, you can easily overfill the tank, and suddenly you have 11.5 + liters in there, and that creates problems.
the oil seeps into the engine, the plugs, and causes havoc. cel lights go on, and all sorts of things happen. not easily sorted out either - you can drain some of the oil, but the seepage and havoc remains.

this happened to me on my own and the one i bought for my mother.

i mention it because it goes undetected sometimes.

 

According to the techs at Ferrari LA, when starting the car, the check valves help to keep the pressure in the fuel lines to eliminate the rough starting.

 

I think the problem, Will, is your stock exhaust. It's far too quiet.



(I'm completely kidding. I know the Original Poster in real life.)

Matt

 

Try this fort he CEL:
First make sure all the plug wires are making good contact with the plugs and all the plugs a firing correctly.
If all checks out fine, remove the corresponding air flow mass sensor and clean it with the appropriate spray.
Drive for a few miles and if the light goes off it means it was dirty.
If the light comes back after some time, it means it is time to replace the air flow sensors (because they are old and unable to self clean anymore).

 

thanks