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

[LS (lashdeep]

A college buddy's '87 Audi 4000S had this same cold start issue. He ended
up jumping the Thermo Time switch with a generic toggle installed inside
the passenger compartment. When a cold start was needed, you'd flick the
toggle switch to close the circuit, then crank as normal to start, when it
was done, flick the switch back.

It was a clever, low buck solution befitting a $600 Audi...

LS

--- Paul Bennett <pbennett [at] macnet.com> wrote:

> 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.
> 
> 
> 
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