Peugeot 406 over revving on idle

Hi
My 406 (1.8 petrol) has literally just started to over rev on idle.
It is usually around the 750 mark but has begin to go up and down the
rev counter from around 2000 to over 3000. it also jerks on
decelerating as if the cables are sticking (but this is not the case
as can be seen from the idle issue).
Has anyone any idea what this might be (Local Peugeot dealer & garages
all shut at mid day saturday - like cars don’t go wrong on a weekend!)
Any ideas would be appreciated.

 

Oop’s
Think I found part of the problem.
Engine was out of oil!!!
Put some in & is running OK now.
Must remember to check this more regularly.
ops

 

I have the same engine in my 405. It is almost certainly the idle control
valve sticking. I clean it every now & then when it plays up. One day I will
stop being a tightarse and buy a new one.
It is right on top of the engine righthand side near the coil pack. Two fat
hoses and an electrical connector.

Bob

 

Except on the 406 it's called a stepper motor and is on the throttle
housing fixed with two torx 20 screws. Remove and clean with brake
cleaner and also spray some cleaner into where it fits. Dry as much as
possible and replace. It may be worth initialising it to the ECU.
Switch the ignition on for 10 seconds, then off for 10 seconds then on
again for 10 seconds then start the engine. You may need to full
throttle it to get it going to get rid of the excess brake cleaner.
Then it should run ok. If it still idles up and down, try the
initialising again but disconnect the battery for a couple of minutes
beforehand.

 

This thread interested me because my 406, which has never been a
problem in this area, has, from the start, had a habit of quietly
reving a bit every 3-5 minutes or so when idling for long periods. You
know -- stuck in traffic. I have a theory that it is something the
engine management system does for some good reason.

Apart from that I will print out Nigel's post and tuck it away in case.