Ferrari Mailing List: Dear Diary - Eliminating 3000 rpm Cold Start Idle

[Paul Bennett (pbennett]

In the understanding portion of fixing my warm start difficulties I learned 
today:

Today's Player - the ElectroValve
Located very near the Oil Filler Stick,  it switches vacuum to the Auxiliary 
Air Valve after the engine warms up.  Hoses are small diameter (1/8"?),  coming 
from the Air Box, going to the Auxiliary Air Valve, a vacuum operated bellows 
device behind the Regulator.

Michel Savard replaced the BIMETAL THERMOSTAT #115652 after first stating 'Cold 
Start Air Valve' which the is bypass around the throttle plate, fixing his warm 
start problem, which is why I'm focusing on it today.  But I MISTOOK what he 
said for the bellows AAV which brought me to the ElectroValve.

The ElectroValve is activated electrically by 12v when coolant reaches 40C, 
providing AirBox vacuum to bellows in the AAV,  KILLING FAST COLD IDLE.

HOW TO: To eliminate the rediculous 3000 rpm cold idle, route the longer hose 
on the ElectroValve directly to the Air Box.  Remove the short hose formerly at 
the Air Box and loop it back to the 'T' on the Elctrovalve.   Some time back 
I'd heard about plugging a hose which probably referred to the AAV output hose 
which raises the idle. There may be other ways of accomplishing this but this 
does work.   

Lingering question-my car always cold started at 900 rpm and didn't rev to 
3000rpm for a full minute. Not important but curious.  By the time I find my 
solution I expect to actually understand CIS.

Tomorrow back to work on what Michel really found as his solution. The book 
states: In some VWs and Audis, a hot -start relay adds fuel by energizing 
cold-start injector during hot engine cranking.  Maybe this is involved.

OK to SKIP this
Re the part Michel replaced,  the book states:
"The Thermo-Time switch controls the open time of the cold start injection 
valve.  The switch senses engine coolant temperature.  The switch contains a 
bimetallic strip that is closed when the coolant temperature is below 35C 
(95F).  This would complete the ground circuit for the cold start 
thermo-switch.  The thermoswitch is closed below15C (60F) allowing the cold 
start injection.  Above 15C the cold start thermoswitch is open, interrupting 
the ground circuit preventing any cold start injection.  

To prevent excessive fuel from being injected, heater coils warm the bimetallic 
switch while the engine is starting.  This causes the switch to open within 12 
seconds regarless of coolant temperature.  When the switch opens, the cold 
start injection valve closes."


Incidentally, I'm working from a borrowed copy of 'How to Understand, Service 
and Modify Bosch Fuel Injection & Engine Management by Charles O. Probst, SAE, 
Robert Bentley Publishers ISBN O-8376-0300-5   AND  a 25 page document from 
Ferrari Training which I've put into MS Word doc format.  Anyone wanting a copy 
of the later just holler.