1989 300E Starting problem

I have a 300E w/217,000 miles. The only issue I have with the car is starting it. Unless it has sat over night, the car will not hold idle upon starting. I have to hold the idle @ 1000rpm for 10 seconds, then
the idle settles down to a noce smooth 600-700rpm. Sometimes this goes away, but the problem has returned. Any Idea's?
Thanks, Thom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Cold start system isn't working. Temperature sensor, time relay and cold start (injector) valve, This is the chain; you need to find which is defective or unplugged.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

He said it starts and runs okay when it has sat overnight. It's the rest of the time that he's having a problem. Doesn't sound like the cold start system to me, unless it's firing when it shouldn't.
I think we need more info., like does it run okay after it's warmed up regardless of starting conditions? What if it's running fine and you shut it down and start it again immediately--does it still go into a bad idle? When you say it won't "hold idle", does it stall? Hunt? What does it do exactly?
Bill Balmer 1986 190E 2.3-16
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Once it is running, it never dies, nor does the idle drop below 600rpm. If I try to start it immediately after shutting it down, it takes about 4-6 seconds of cranking before it fires up, but it will still try to die if I let it. Once it is running, it never dies, nor does the idle drop below 600rpm.
I'm getting ready to give it a tune-up, hoping sme new plugs and other items might help. I got the car from my father, he told me he was running regular unleaded in it. I am running only Shell or Marathon premium in it (the manual says minimum 91 octane), plus I am trying to stay away from methanol/ethanol.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.