Manual Idle vs Automatic Idle
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Manual Idle vs Automatic Idle



Fully agree that properly functioning automatic idle system is
preferable to manifold screws. Mine was improperly malfunctioning.
Sometimes would stick fully open. Sometimes would stick fully closed
(that's when I discovered what those screws are for). Replacement
motor and ECU exceeds $500. Screws are already in place. Guess which
route I chose...

Fast idle is accomplished with an "auxiliary air valve". Extremely
common on other cars contemporary to DeLorean. In fact, mine is used
from a BMW ($5 on eBay).

Originally thought I would also have winter and summer idle speed
settings, just as I do on my Lincoln re-carbs (Edelbrock wants $80 for
an A/C solenoid!), but find that simply leaving aux air valve open
works just as well. Really only need in city driving.

In your defense, while Volvo 260 used manual idle speed circuit, a
1990 760 I recently popped hood on had an idle speed motor that looked
just like DeLo, in exactly the same place.

I think it's important to understand manual idle circuit for diagnosis
if nothing else. How else to rule out idle speed motor as a potential
problem?

My experience has been that rocket science doesn't age well. On my
Lincolns, for example, automatic headlight ativators and dimmers are
usually DOA. Is a challenge just to keep cruise controls properly
functioning. Would argue is unrealistic to expect ALL DeLo ECU's and
idle speed motors / Lamda valves to function today as they did 22
years ago. Some do -- more power to them. But an owner shouldn't
assume he or she will be so lucky. Running problems may well be
attributable to a failed system. Mine was (and I don't even have Lamda).

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "David Teitelbaum" <jtrealty@xxxx> wrote:
> When you disable the idle speed motor you give up a lot. The motor
> will no longer run faster when cold and if you turn on the A/C or run
> a lot of accessories like headlights and rear defogger the ISM cannot
> keep the idle speed stable. Under high loads at idle the ISM will keep
> the idle at 775 rpm. The fixed metering screws cannot adjust to
> varying loads. In addition in some states you are not supposed to
> tamper with anything that can affect the emissions. Some states do
> check these things. For your own sake and that of a future owner it is
> usually best to keep the car as origional as you can. It is often
> harder to make changes than to try to stay origional.
> David Teitelbaum
> vin 10757
> 
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "content22207" <brobertson@xxxx> wrote:
> > Mention this to list with trepidation because it usually ignites flame
> > war, but IMHO is important:
> > 
> > At same time JZD was messing around with idle speed motors, Volvo just
> > used brass screws already built into PRV to set idle. Low tech, yes,
> > but less subject to problems. I think every owner should know how to
> > use in case automatic idle system fails or needs diagnosis, if






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