1983 280 SL- funny cold strating

[zakkkk]

My car will sit for 2 or 3 weeks in the garage between weekend drives. I put about 500 miles a year on the beast.
I have had it for 4 years or so and it always cold started a bit funny. But with warm or hot starts it fire up immediately on half a crank and runs like a tiger.


The usual funny cold start goes like this- crank the starter and engine fires but chokes and sputters for 10- 15 seconds but does not stall then smooths out and then runs fine


If the car sits for a month or it is very humid ( for some reason)it starts but chokes and sputters until I can drive it for a mile or so, then all is perfect.


I have learned the trick ( from this forum) about turning the ignition key back a click from the start position then forward a click a few times to allow the fuel pump to pump in more fuel to the system before the turning the key for engine start and that has almost always solved the problem.


But on Saturday last it was the worst. Even with the above clicking the key for more fuel , the engine would start then sputter and die. It would not take fuel when I depressed the accelerator. It would just die. Finally after 10 minutes of trying to start it I was able to keep the engine running by feathering the gas pedal, but it run poorly and choked under 2000 rpms and had a low idle until about 15 miles of high way driving. Above 2000 rpms it ran fine but if the rpms dropped below 2000 rpms it would choke and sputter. Then it seemed to clear it's lungs after the 15 miles and she ran perfectly at all rpms.


Another symptom now is that the idle is a bit shaky, like a cylinder is slightly misfiring.


At first I thought that fuel was running back to the gas tank when it sat for 2 weeks or so which led me to believe it was a air leak somewhere in the fuel lines. But now there was this prolonged congestion.


Funny the car run and started perfectly all day Saturday and again the first thing Sunday morning it started like a shot.


I can't figure what is happening. Air leak? Clogged fuel filters/ fuel line? Clogged injector? I don't think it is spark or electrical related. During all the choking and stumbling there is not a bit of smoke or smell of gas and engine Temp is a solid 180 c and never rising.


I have heard that the M110 engine and ignition/fuel injection were tricky to get perfect so I hate to monkey around with it.


Any insight or advice is welcomed.


thanks,
jz