1985 280se wont start unless you have throttle wide open

Clean the Throttle Body and MAF with Cleaner. That causes rough idle.

Also drop a bottle of Fuel System Restorer into half a tank of gas.

More ideas here, but start with the above.

https://www.google.com/search?q=2005+chrysler+town+and+country+rough+idle

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Had a s10 one time and had similar problems turned out after I got rid of it a friend figured it out it was the computer and the Catalac converter how ever you spell it hope this helps Merry Christmas

My first guess would be a leaking fuel pressure regulator or a problem with the injector grounds. The injectors may be "on" too much.
Is the check engine light on when you can get it running ?

clearly sounds like fuel starvation, I would be looking at the throttle body, they need servicing every couple of years, they fill up with like grease and block tick over hole.....

How old are the spark plugs? What brand and gap are the spark plugs? How old is the fuel filter? You should also do a fuel pressure test.

it has a dirty throttle body. get some carb cleaner and a tooth brush.remove air cleaner hose at the throttle body. block open throttle to wide open {engine off of course} or have someone hold it to the floor.spray cleaner into body and scub with tooth brush especially were the throttle plat touches the bore when at idle and the throttle plate itself.spray brush,spray,brush. put hose back on and start engine. you might have to give it some gas to atart it then its going to run rough for a few seconds but it will clear up.slowly lower foot from gas pedal and allow to idle.put in reverse let run in reverse for a few seconda do the same with drive.it has now began to learn what position the stepper motor should be in when throttle is not depressed.it may stumble a couple of times at sops but will soon correct itself

1988 ranger 2.9 runs great cold then after a few minutes when warmed up hesitates with intermittent black smoke from the tail pipe until i hit the the throttle then clears and will repeat this behavior...

sounds more like the electronic control module

try checking your fuel tank for sediment it may be clogging the fuel pump and when it dies it falls away then when you start up again it gets sucked up

Sounds like a large vacuum leak,low fuel pressure,fuel pressure regulator failure, idle air control valve stuck open,plugged fuel filter.Also check for good consistent blue spark at spark plugs or jumped timing chain.Hope this helps!