1999 406 2L Petrol Idle Issues

Talk about the 406's electrical system, what wires do what, how to add extra functionality, etc.

Moderator: Moderators

Post Reply
406Olly
Newbie
Posts: 2
Joined: Mon Dec 11, 2017 4:41 pm

1999 406 2L Petrol Idle Issues

Post by 406Olly » Mon Dec 11, 2017 5:19 pm

Hiya,
Just bought my first 406 after seeing one up for sale in the local shop window for a (or what seemed like a) steal. 54k, full service history £300! What could go wrong. Very impressed with how it drives (or drove).
Got it home only to realise in cold weather it doesn't like to run. The engine starts lovely and sounds great but if you take your foot off the pedal it dies instantly.. After a bit of research I discovered that it's most likely the idle control valve/stepper. So I bought a new one and put it in and since then it has been even worse. Before if you ran it a bit it would stay running but not anymore, perhaps down to the change in weather though. It seems asthough the idle control valve is just shutting the airway off completely and not opening again. If I remove it it is completely out.
If I take the stepper motor out and push it all the way in then install and reconnect it it will run at high revs and gradually slow down the revs as the motor finds its self but will eventually cut out the engine or will go to very low revs. If I then apply a bit of throttle the revs increase and when they come back down it stalls the engine.
I have tried manually opening the control valve and just leaving it disconnected and it seems to run ok, but the idle speed obviously then depends on conditions. If I then reconnect the idle control valve socket it will bring the revs down gradually and eventually die again.
I Have also installed the valve and left the battery disconnected for a few hours to reset the ecu before starting. Same thing happens again. No faults are appearing on the dash bar the Air bag light occasionally..
Bought a OBD2 diagnostic machine (just a cheap one) but that won't recognise the ECU even though it apparently should..

This is the car here https://www.youtube.com/watch?v=0NNbUoW2pY8

Any help or insight would be very helpful. Am considering attaching some sort of manual choke cable to it :lol: It's such a shame the thought of scrapping such a low mileage car.. I was hoping to use it through the winter as my Volvo 240gl is a bit sketchy in the ice.

Thanks
Oli

Post Reply