Surging Engine After Cold Start

[Robski]

Hi, my 1971 350SL (with Bosch D-Jetronic fuel injection) starts and runs no problem, but when the start is from cold it will run well for around 30 seconds, but then start to surge between 1000rpm and 2000rpm for around a minute before settling down to what I guess is a normal high (cold) idle speed that decreases down to 750rpm once its fully warmed up.

Does anyone know (or can help me diagnose) what may be the problem here?

Robski

 

[ajlsl600]

has that car a seperate injector in the manifold somewhere thats playing up.or its drawing air from somewhere for a while.. would say a fuel air issue . i remember some fuel injector ,petrol systems used to have another injector in the manifold for the coldstart

 

[malcolm E53 AMG]

This could be useful it sounds like the auxiliary air valve there is a troubleshooting section

http://w107.pbworks.com/f/DJetronic.pdf

 

[ajlsl600]

so it does have a cold start injector. now on some systems like bloxxy lr the cold start injector was 6v whilst engine running injectors were 12v . tell me that was,nt just so you never had a spare !! if thats not the case here, maybe you can swap them? or just pull the plug and see the difference.OP says it does settle down , struggling to see where air leak that heals itself regularly and after a few moments would be. and if so it would likely be electricaly controlled . too quick to settle for it to be thermostat controlled.