Idle control module - function/modify signal?

[Rich M]

Albert,
I think the 'module' you speak of is the canister purge valve (tank vent). I
believe it is just that - a valve; inlet from (tank vent) charcoal canister,
outlet to intake manifold, 2-wire connection to the operating coil (one wire
is ignition switched +12V feed, maybe red/blue, the other is controlled by
the ECU, maybe brown/red).
As far as the intended operation is concerned, I can quote from a UK Haynes
workshop manual:
"the charcoal canister is purged under ECU control through the fuel tank
vent valve. To ensure that the engine runs correctly when cold and/or
idling, and to protect the cat. converter from the effects of an over-rich
mixture, the valve is not opened by the ECU until the engine is under
partial or full load. The valve is then modulated on and off to allow the
stored vapour to pass into the inlet"
Have you tried clamping off the hose which goes to the inlet manifold -
maybe the vent valve is leaking or open at the wrong time?

Is the idle speed maintained OK once the engine is hot, with varying
electrical load for example? Is the idle speed contol air valve working OK?
(pinch off the hose from IAC valve to intake - idle speed should drop). I
have heard of the Idle speed valve (IAC) getting sticky and sluggish, it is
a rotary valve and maybe the spool is not able to open fast enough to
maintain idle speed when you lift off and the engine speed falls to idle.

Has the base idle (throttle plate setting) been adjusted properly?
Adjust with engine at operating temperature. Pich off the IAC valve hose
that goes to the intake. Adjust the idle speed by means of the throttle
plate stop screw to 650rpm (maybe only just runs at this speed:-) ), release
the hose clamp - this should then raise the idle speed to approx. 850-900
rpm due to the action of the IAC valve. The ECU should then be able to
maintain idle speed under varying load conditions (electrical load, air
conditioning etc) by adjusting the position of the IAC valve.

The vent valve which you originally asked about should have no part in idle
speed control, it should be shut at idle, the IAC valve (aluminium
cylindrical valve, 2x 1/2" hose connections, 2-pin electrical connector,
usually mounted on top of the engine above the injectors) does all the idle
speed air control.

I'm rambling... I'll get my coat...
Rich.

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Aribert_Neumann at magna.on.ca
> Sent: 08 June 2000 13:51
> To: diy_efi at diy-efi.org
> Subject: Idle control module - function/modify signal?
>
>
>
>
> I am looking for info on the basic concept behind an idle control
> module as used
> on a Bosch Motronic (specifically M1.5).  THis unit (about 1 in.
> cubed) has an
> electical connector with 2 leads and 2 vac ports - one to the
> cannister the
> other port on the intake manifold downstream of the throttle plate.  I am
> looking for ways to modify the signal back to the ECU.  Since I
> am in North
> America and the engine management system is off of an
> Opel/Vauhall, I am very
> reluctant to split open the case to see what is inside due to the
> difficulty in
> getting spares.
>
> Background:  I have adapted the Motronic M1.5 system from a 2L GM
> Europe engine
> onto a 2.3L Isuzu engine.  So far  the Isuzu vehicle has
> completed about 1500
> uneventful miles since the conversion from the carb.  Only
> problem is the engine
> will die when lifting off of the throttle for the first several
> minutes/ miles
> of use.  Once the engine warms up then the idle is good.  I have
> upped the idle
> by 100 rpm by adjusting the throttle plate stop and added an 1300
> ohm resistor
> in line from the water temp sender.  Both changes improved the
> condition but not
> enough.   I do not have the skills to modify ECU codes.  Other
> suggestions?
>
>
>
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