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

["David Teitelbaum" <jtrealty@xxxxxxxxxxx>]

As I see it you have 2 control loops, the idle speed control and the
Lambda control. They are indirectly coupled through the interaction of
the motor itself. Since they act differently during warm-up and are
not syncronized to each other you get all kinds of weird effects. Add
to that any unbalance in the motor like a cylinder with low
compression, a dirty fuel injector, a dirty spark plug, etc, and you
have the "hunting" which is amplified in the hysterisis of the
uncoordinated control loops. Everyone seems to neglect the importance
of having a balanced mechanical system FIRST. If the compression of 
all the cylinders is not very close (never mind what the actual # is)
it will never idle smooth. The idle system and the Lambda system won't
correct for cylinder imbalance. This is also why vacuum leaks are so
important for smooth idling. They usually tend to cause some cylinders
to run leaner than others adding to the imbalance. Now you start to
realize some of the benefits of an engine management system where all
of these variables can be controlled with some syncronization. I have
seen too many Deloreans where the Lambda isn't even running! It does
make for a smoother idle when warm but a noticable lack of power and a
large stumble on acceleration. I have also seen too many cars without
the plug over the mixture screw. That leans out the motor with "false"
unmetered air, a double whammy. Then they have the air bleed screws
open to try to get a higher idle. Undo all this stuff to get
everything to run right and you see why it happened. The motor runs
rough because it is not in "balance" so the "mechanic" starts playing
with what he can. BTW I also believe too many Deloreans have seals on
the fuel injectors that should be replaced. Once they get hard they do
not seal well and leak "false" air. You can tell easily, the injectors
are so loose they just come right out and the seals are like rock, not
rubber. To set up a Delorean takes some knowledge and a lot of
attention to small details. Once set up they hold their settings well.
That is till something wears out or ages. The fuel system should never
need to be touched if it stays clean. The main reason not to mess with
the mixture screw to "fix" anything.
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxxxxxx, "Elvis Nocita" <elvisnocita@xxxx> wrote:
> 
> 
> 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.
>








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