Re: [DML] Re: Tuning Idle Speed Circuit. (John Hervey)

["Rustproof" <Rustproof@xxxx>]

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
>
>
>
>
>
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