Does anyone know how the Idle control valve works on a Citroen
Synergie 2.0 petrol.  The revs are dropping low and sometimes stalling
at junctions.  I cleaned up the IAC and with it removed from its housing
turn on the ignition and I can feel 3 pulses from the unit but the
plunger does not move.  I was told that the pulses I hear will be the
stepper motor making sure it's at the start point so I won't necessarily
see the plunger move.  Do these only move when you start the vehicle and
if so is there any way to check that it's working ok.

"John"  wrote in message
news:3o1abmF3n3k6U1@individual.net...

> Does anyone know how the Idle control valve works on a Citroen
> Synergie 2.0 petrol.  The revs are dropping low and sometimes stalling
> at junctions.  I cleaned up the IAC and with it removed from its housing
> turn on the ignition and I can feel 3 pulses from the unit but the
> plunger does not move.  I was told that the pulses I hear will be the
> stepper motor making sure it's at the start point so I won't necessarily
> see the plunger move.  Do these only move when you start the vehicle and
> if so is there any way to check that it's working ok.


AFAIK this is a plunger type (standard type) ISCV which is driven out by a
solonoid and retracts via a spring.

With the ignition turned on to position II the plunger should move out to a
start position. -The exact position being determined by engine temperature,
and trimmed by the ECU's learnt adaptive values.

With the unit assembled but removed from the vehicle, you should be able to
see through it to check. (unless this is a late car with the plastic
manifold)

Tim..

"Tim.."  wrote in message

> AFAIK this is a plunger type (standard type) ISCV which is driven out 
> by a
> solonoid and retracts via a spring.
>
> With the ignition turned on to position II the plunger should move out 
> to a
> start position. -The exact position being determined by engine 
> temperature,
> and trimmed by the ECU's learnt adaptive values.
>
> With the unit assembled but removed from the vehicle, you should be 
> able to
> see through it to check. (unless this is a late car with the plastic
> manifold)


Cheers Tim.  It does looks similar to ICV's that I've cleaned on other 
motors which have operated in the same way you say but this one just 
makes a click noise but the plunger does not move even if I try to 
pull/push it.  When I cleaned and replaced the valve the engine started 
but would then not even idle at all.  After a while it started to idle 
as it did before at around 900rpm but very lumpy and hunting.

What I was thinking is that when I disconnected the multiplug from the 
ICV the ecu reset itself into default mode which (if the ICV was not 
working) made it not idle at all when reconnected until the ecu had 
re-learned itself and was trying to keep the engine idling to compensate 
for the faulty valve. I'll try and get hold of another ICV and see what 
that does.  BTW it does have the plastic inlet manifold.

> Cheers Tim.  It does looks similar to ICV's that I've cleaned on other
> motors which have operated in the same way you say but this one just
> makes a click noise but the plunger does not move even if I try to
> pull/push it.  When I cleaned and replaced the valve the engine started
> but would then not even idle at all.  After a while it started to idle
> as it did before at around 900rpm but very lumpy and hunting.


My limited experience with idle bypass valves is that the garages will go on
for ages saying it is this component or that component and the ECU says it
is the other component. However, if you just ignore them and just replace
the idle valve, it generally solves the problem. I've never had success
cleaning them, although I've only had the problem twice, so it isn't a
particularly scientific sample size.

Christian.