[DML] Re: Tuning Idle Speed Circuit.

["Harold McElraft" <hmcelraft@xxxx>]

CO at less than 1% is too low in my experience; CO2 at 14.1 is too 
low also. Try 2% CO. This will probably yield a CO2 reading around 
15.0, HC should still be near 0, NO will still be low too. Run and 
idle should sinc up and you can still pass an emmissions test with 
flying colors.

Harold McElraft - 3354



--- In dmcnews@xxxxxxxxxxxxxxx, "Rustproof" <Rustproof@xxxx> wrote:
> John,
> The engine was set up at normal operating temperature with both 
fans running
> and A/C off. I have set the CO using an exhaust gas analyzer. The 
method of
> adjustment was to simply let the tool sit in the screw head 
without any
> downward pressure turning 1/16 to 1/8 at a time. I can't seem to 
set my idle
> at 950 with the O2 sensor plugged in. If I attempt this it swings 
wildly as
> if it wants to stay near 750. I have been making the idle 
adjustments using
> the curb-idle screw on the throttle linkage. I have noticed that 
if I use
> the idle adjustment screw on the throttle body intake manifold, 
(The slotted
> brass one of the three closest to the throttle plates) it has no 
effect on
> the idle speed at all. As a matter of fact, none seem to have any 
effect at
> all ...with or without the O2 sensor connected! The closest I can 
get to a
> stable idle is a swing of 25-50 rpms in either direction. However, 
even then
> the engine idles very rough. I have checked for all possible 
vacuum leaks
> and there are none. The timing is 13 degrees BTDC on the money. 
(at 750rpm)
> There is no vacuum present at the distributor vacuum advance. The 
lambda
> system appears to be working as is the CIS. That is to say that 
the air
> valve is actuating in both directions and the Lambda system reacts 
to the O2
> sensor signal. The full throttle switch is functioning. ( when I 
press it,
> the idle will settle right down.) The idle microswitch is 
functional and
> adjusted properly...well as properly as I can get it with this 
idle problem.
> At startup on a cold engine, the car turns right over but runs 
very rough
> until it warms up a bit. It idles rough and boggs down if you 
attempt to
> give it some throttle. Once warmed up, it becomes very responsive 
and seems
> to drive O.K. Thereafter, it is easy to start and accelerate but 
the idle
> remains poor.
> 
> Thanks,
> Rustproof
> vin 1559
> 
> ----- Original Message -----
> From: "John Hervey" <john@xxxx>
> To: <dmcnews@xxxxxxxxxxxxxxx>
> Sent: Saturday, August 30, 2003 1:55 AM
> Subject: RE: [DML] Re: Tuning Idle Speed Circuit. (was: Re: idle 
problem)
> 
> 
> > Rustproof, See below.My 2 Cents.
> > John Hervey
> >
> >
> > -----Original Message-----
> > From: Rustproof [mailto:Rustproof@xxxx]
> > Sent: Thursday, August 28, 2003 9:36 AM
> > To: dmcnews@xxxxxxxxxxxxxxx
> > Subject: Re: [DML] Re: Tuning Idle Speed Circuit. (was: Re: idle
> > problem)
> >
> >
> > Having taken all the advice I could get from the list and the 
archives, I
> > have attempted to set up both the CO mixture as well as the CIS 
idle. This
> > was fiddled with by the previous owner and never properly reset. 
I set the
> > (CO Mixture Screw) air/fuel mixture using an exhaust gas 
analyzer at
> 14.1:1
> > with CO emmission at less than 1%. Idle set was 750 and varied 
about
> 50rpms
> > high and low.
> >
> > ( First I would adjust by ear and set the idle at 950. Makes 
sure the
> lower
> > idle speed screw on the throttle body lever is resting on the 
stricker
> plate
> > and then the upper screw is turned in about 30 thousands and 
hitting the
> > microswitch to activate the idle speed motor 1st..)
> >
> >
> > The frequency valve could be heard at idle at a relatively
> > constant and stable pitch. ( Good, it should be.)
> >
> > The engine appeared to run very smoothly.
> > However, upon shutting it off, it would not restart! I then 
advanced the
> > mixture screw by 1/8th turn intervals clockwise until the engine 
was able
> to
> > start. The idle was erratic and fluctuated several hundred RPMs 
hunting
> > wildly. The frequency valve buzzed on the lean upswings and was 
silent on
> > the downswings. I then adjusted the CO screw (by ear) until the 
engine ran
> > smooth again but I could see by the analyzer that it was running 
on the
> rich
> > side to get it to settle down. I then set the idle again to 750. 
This time
> > the idle remained on 750 exactly with no fluctuation at all but 
the
> > frequency valve remained silent. I assume that this is due to 
the very
> rich
> > mixture. The engine seems to run fine set like this but I 
realize that I
> am
> > essentially nullifying the lambda system with the over-rich 
mixture.
> > ( The Lambda ECU is electronicly set to enrich untill the 02 
kicks in,
> That
> > why it's running rich.)
> >
> > The engine has been checked methodically and no vacuum leaks can 
be found.
> > All
> > o-rings, tubing and fuel system parts including pump, 
accumulator and hot
> > start kits are new. The engine has only 8,000 miles on it.
> >
> > ( When you adjusted the 02 about 1/8th turn, Do you know what 
you did. Was
> > the engine hot,and did you push down on the tool or just let it 
rest in
> the
> > screw head and turn.)
> >
> > I was hoping that someone on the list with a pefectly 
operationg system
> > might answer the following questions:
> >
> > 1. At idle, should the frequency valve buzz constantly and 
steadily?
> > ( If everything is properly adjusted my answer would be yes.)
> >
> >
> > 2. With the O2 sensor unplugged, I am able to set up everything 
exactly to
> > spec. and the engine runs smooth and perfect. As soon as I 
reconnect it,
> it
> > hunts wildly again and I am forced to adjust the CO mix again to 
get it to
> > settle down! Why is this happening?
> > ( Your doing a manuel adjustment and the 02 does it 
electronicly.The 02
> it's
> > going to monitor it every step of the way which is what it's 
supposed to
> > do.You just have to get to the 14.0 to 1 so there will be very 
little
> swing
> > by the 02 to the Lambda ECU to the FV.)
> >
> > 3. At 750 idle, should the CIS adjust to compensate for the A/C 
load or
> does
> > the idle normally drop 100 RPMs.
> > ( The CIS,??? has nothing to do with the extra load.Not for sure 
what you
> > mean Should the CIS compensate.)
> >
> > Your input will be greatly appreciated!
> > Thanks,
> > Rustproof
> > Vin #1559
> >
> >
> >
> >
> >
> > > To address comments privately to the moderating team, please 
address:
> > > moderators@xxxx
> > >
> > > For more info on the list, tech articles, cars for sale see
> > www.dmcnews.com
> > >
> > > To search the archives or view files, log in at
> > http://groups.yahoo.com/group/dmcnews
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > >
> > >
> > >
> >
> >
> >
> >
> > To address comments privately to the moderating team, please 
address:
> > moderators@xxxx
> >
> > For more info on the list, tech articles, cars for sale see
> www.dmcnews.com
> >
> > To search the archives or view files, log in at
> > http://groups.yahoo.com/group/dmcnews
> >
> > Your use of Yahoo! Groups is subject to 
http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
> >
> >
> > To address comments privately to the moderating team, please 
address:
> > moderators@xxxx
> >
> > For more info on the list, tech articles, cars for sale see
> www.dmcnews.com
> >
> > To search the archives or view files, log in at
> http://groups.yahoo.com/group/dmcnews
> >
> > Your use of Yahoo! Groups is subject to 
http://docs.yahoo.com/info/terms/
> >
> >