Re: Tuning Idle Speed Circuit. (was: Re: idle problem)

["content22207" <brobertson@xxxx>]

Is actually a bit more sophisticated than that:

Screw closest to air sensor plate lets air into idle circuit. Is where
final idle speed will be set at end of process.

Middle screw balances passenger side of engine.

Screw closest to U pipes balances driver side.

Need to balance both sides of engine for best idle. Will be similar
number of turns, but not necessarily identical.

Standing offer remains: have manual idle circuit setup procedure from
Volvo newsgroup I will send to anyone interested
(brobertson(at)carolina.net).

Fully agree that properly functioning automatic idle speed circuit is
hottest thing since sliced bread. Unfortunately mine wasn't
functioning properly. Actually became outright schizophrenic. Don't
miss it one bit.

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "therealdmcvegas" <DMCVegas@xxxx> wrote:
> --- In dmcnews@xxxxxxxxxxxxxxx, "checksix3" <jetjock11@xxxx> wrote:
> > ...I have yet to see the proper way to set up the idle speed system 
> > (the Bosch recommended method) in any post or archive.
> <SNIP>
> 
> I know I've seen the procedure before, but I can't remember if it was
> here, or off list in a private e-mail. but I believe the procedure was
> to open the first/main screw by giving it 4 equal turns, then give
> each throttle tube 2 screws. Then just fiddle with the main screw to
> set the idle.
> 
> >As long as you 
> > have no air leaks and your CO is set closely this will solve all idle 
> > hunting...period. Some airflow trough the throttle body and metering 
> > plate is required for the system to work properly. This is obvious if 
> > the conductance of the system is measured. 
> <SNIP>
> 
> Well, um. This is true, but only dependng upon your point of view. The
> Idle Speed Motor does a fine job of setting the idle speed, and of
> maintaing it. But as I found on my car, only when you drive gently.
> 
> If the engine is at a high rev (usually about 4K or more RPMs), then
> when you push the clutch in to drop (or let off the gas on an auto
> from my experience), the RPMs will fall VERY quickly. In my case, I
> had two senarios: I'd would either kill the motor occasionally, or
> mostly I would just strain the hell out of my electrical system. Dim
> lights, dropping volts, you name it. This was compound at night when I
> had the clearance and headlights on. And if the A/C was running, then
> forget it. I could drop my RPMs low enough that battery light would
> flicker, of not kill the motor again.
> 
> Now I had to compensate on my car to bend the bracket for the Idle
> Speed Microswitch, and extending the stop bolt on the throttle
> assembly. This now causes my Idle Speed Circuit to trip early, and
> activate the ICM so that it will open early enough so the engine
> doesn't dip too low, and I keep my electrical system stable.
> 
> However, there has of course been a trade off. I now have no gradual
> powerband. Gently pressing my acellerator pedal, The ISM then tries to
> compensate for a "fast idle" by choking my engine, rather than
> allowing me to add the extra airflow to my acelleration. Once the
> Microswitch is deactivated, my RPMs then jump to 1,500! Not really
> fun, since it makes my clutch a bit "grabby" IMO, but nothing really
> damaging. Just annoying.
> 
> The other problem with the Idle Speed Circuit is that it doesn't like
> to work well with a motor that's not properly tuned. If you do have a
> vaccum leak, or you're running rich, then the idle seeking/hunting
> will of course occur (that's the LAMBDA system cycling). However, the
> Idle Speed Circuit seems to compound this problem. Instead of suttely
> compensating the ISM to gently stabilize the idle, it likes to panic.
> Anyone who's had a vaccum/mixture problem, and has tried to start
> their car on a cold morning know exactly what I mean. The ISM goes
> "WOT" to increase the speed. And when it gets too high, it goes
> "Choke". And when the RPMs drop too low, it goes "WOT" again. This
> cycle occurs until the engine finally warms up and/or the fuel mixture
> is balanced.
> 
> 
> Now with this said, don't think that I'm putting the stock Idle Speed
> Circuit down. On the contrary, I think that to remove it is perhaps
> one of the worst mistakes that you could make. However, I do feel that
> as great of a system that it is, that it needs to be supplemented. And
> that is where setting the Engine Idle Speed manually comes into play.
> 
> By setting the initial Engine Idle Speed manually with the 3 brass
> screws, we create a "pillow" of sorts for the engine speed. The idle
> should stay far more stable. When the RPMs drop hard, the engine isn't
> going to have to wait for the ISM to activate, and open up to feed the
> engine air. When cold starting, the idle seeking should be kept to a
> minimum by way of a solid supply of air keeping the RPMs from dipping
> too low. And of course, strains on the cars electrical system could
> greatly be quelled. Extending the life of your Alternator and Voltage
> Regulator, and keeping the motor from stalling out in some cases. And
> of course, you can keep the lights bright. Another thing is that this
> should hopefully reduce engine noise a bit. When my motor is cold, the
> sound of extra air rushing thru the ISM, and the brass tube is quite
> noticeble.
> 
> 
> Now, if there is any downside to utilizing the Manual portion of the
> Idle Speed Circuit, then please, let me know. I myself really don't
> see any harm in using it. Only benefit. And everything that I've read
> against it has been mainly along the lines of, "You shouldn't need
> to.", and "The manual doesn't say it's nessisary." I understand both
> these points, but in using the Brass Screws, I really only see how it
> can improve upon the existing system.
> 
> -Robert
> vin 6585 "X"