Rough starting/running until 173-175F

[bikerjosh]

I can’t be the only one experiencing this with my van. Issue started out of the blue. When I start my van after it has sat for a day it fire up and after 3-5 seconds starts running really rough and will die unless you bring the revs w/some extra skinny pedal. It sounds really strange like it is on.y running on 2 or 3 cylinders and if you try and drive it, it has very little power and doesn’t want to go over 2500 rpm. I have tried driving it slowly on level ground (cause it doesn’t feel like it make it up any hill). Once the temp on my digital water gauge hits 173-175F, the motor comes out of its stupor, sounds different, has full power and will idle on its own when you come to a stop. It will run like that the rest of the day w/o any problems, even after little it stop for 10 minutes.
Any ideas from the collective? Vehicle specifics: 87’ 4wd, 5 spd cargo. Thanks Josh

[JPERL]

EFI Water Temp Sensor Possibly?

[kamesama980]

does it feel like a dead miss? could be distributor or ignition wire issues. I've had that be temperature and humidity related.

water temp sender was my first thought, if it's failed just right, it could be telling the ECM the engine's warmer than it is thus a lean-roughness issue till reality matches the sensor.