e39 cold surging and airbag light.

1st problem! my 523 (M52TU) has a problem when the engine is stone cold. It surges on very slight throttle. At idle it's rock steady and if I nail it, it revs through cleanly.

The easiest way to describe it is if I start it up and move it a short distance slowly. It will surge, making the car kangaroo slightly. If I drive it normally it's fine. Leave it ticking over for 2-3 mins and it'll be fine, problem disappears. Drive it to the end of the road, problem gone.  

I can live with it but a) it would be nice to fix it and b) I want to sell it so I want the car to be right when it goes.

2nd problem!! The airbag light is on constantly. When I start the car it goes out for under a second then comes back on with a click of a relay. Anyone know what it is.

Cars a 2000 "W" 523i auto

Thanks in advance.

Trevor

Forgot to say that if you take your car to somewhere where they have a diagnostic system they will be able to tell you exactly what is wrong.

I do not think either can be done DIY as you need the light reset by a diagnostic system.

Oops sorry just thought about your other problem,could just be the car has a built in safety feature in that when you start the car it goes into sport mode for the 1st couple of minutes i think to warm the car quicker?

In the cold weather you normally warm the car for a few mins so dont notice it so much.

Both the e39 and the e34 i had did the same.

Trevor

My Vauxhall Senator 3.0i 24 V auto surged when cold.

1 No. new lambda sensor cured it. 2 No. required on my M52 523i, not sure about the M52 TU blocks.

The car wont be in sport mode when cold, more likely will hang on to first gear for longer than normal when cold.  Most autos do this until engine warms up a bit. 

Did your airbag light come on after moving the drivers seat back or forth?  Chances are that the weak electrical connector under the drivers seat for the seat belt pre tensioner system has come loose and caused the fault light.  This was exactly the case on my E39.  My fiancé moved the car so had to move the drivers seat and next time on ignition start - airbag warning light caused by the seat belt pre tensioner wiring connector working loose.  This requires, as Jamie correctly identified, a diagnostic machine to reset once the fault has been cured.  Very common problem on E39s!  Some garages will charge a hours labour costs to diagnose and reset any such faults so be warned what only takes 20 mins will cost as much as 60 mins as they charge you for the use of the diagnostic machine!

HTH

Andrew