Re: [DML] Re: Couple Questions- Coolant System & Idle

["Elvis Nocita" <elvisnocita@xxxxxx>]

Harold,

you are right up to one point - the idle speed motor is not too slow -
instead it is too fast. The engine can't follow the reaction of the 
idle motor, especially when it's cold and the mixture is set rich.
You can try it yourself while playing with the throttle spool on the 
just started cold engine. Open and close it fast (let's say within a second)
and watch the reaction of the engine.
Do the same test a few minutes later when it has warmed up a bit and you
will see, the engine reacts faster on changes of the throttle.

There are basic rules about control loops. With the wrong setup, 
the control loop becomes an oszillator - and this is exactly what 
we have. 

Elvis & 6548 - soon back on the road

> 
> 
.....
> As for the idle when cold, there are few D's that will idle 
> completely stable at a cold start. Usually the colder it is the more 
> likely the "hunt" for the idle speed. Basically the idle speed motor 
> just can't react fast enough. Since the engine is "tuned" at 
> operating temperature - as the engine gets cold sensors turn on some 
> turn off the fuel pressure regulator bi-metal arm contracts, etc. In 
> short, lots of things change. Continuity of components is lost. That 
> is not to say that something may be out of adjustment or faulty if 
> things do not stabilize after a minute or so (usually when the bi-
> metal arm in the fuel pressure regulator warms up) - but, some hunt 
> is perfectly normal. You may be able to get the hunt to slow by 
> changing engine speed with a tap of the gas peddle.
> 
> Harold McElraft - 3354
> 
> 

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