Help, W123 shakes foron startup

[Serusa]

Help, W123 shakes on startup

Hello,
I am fairly new to this forum and this is my first post.
About a month ago I acquired a 1985 w123 230e with 66k on the clock which is a pleasure to drive. In the last week, every time I start it in the morning it starts without a problem but then the revs will fall to about 500 and it will shake and shudder for about a minute. When it warms up a bit, the revs will stabilise at about 900 and I won't have the shakes again the rest of the day unless I don't drive it for several hours. My regular mechanic is scratching his head and I have no mechanical knowledge whatsoever. Please help.

 

[grober]

If your car has the M102 engine with Jetronic K fuel injection it sounds as if your Auxilliary air device is not working. On engine startup an extra injector provides more fuel but this only lasts a few seconds after that frictional loses of a cold engine mean it needs to increase idle speed. the injection system does this by bipassing the throttle butterfly viathe auxillary air device. Other possibility is that that your warm up regulator isn't working properly its what richens the mixture till the engine warms up.
see the relevant sections here.
http://www.dmcnews.com/Techsection/Bosch K-Jetronic Fuel Injection Manual - boschtech-12d.pdf

 

[Serusa]

Thank you very much.