At idle the engine is rough and I can hear some weird noises inside the engine as if something was loose. The engine seems to have adequate power when driving except for the occasional mild hesitation when accelerating from stop. Now what it does not like at all is to stop at intersections, the truck shakes as if it does not want to stop or is not firing on all cylinders.
The previous owner says the engine was re-built from the crankshaft up 35,000 miles ago. I did a complete tuneup (spark plugs, cap and rotor, cables, PVC valve, and pick-up coil). Several vacuum lines were disconnected and I re-connected them as much as I could based on the diagram under the hood (some of the lines from the char coil canister and the purge relays (which I have difficulty identified) are not connected. But it doesn't really matter all that much what I do with the vacuum lines, including from the EGR, these symptoms don't really change all that much. The idle relay seems to be seized but is no where near where it can affect the throttle, I have tried it connected and disconnected with no difference. This model does not have an IAC as far as I can tell.
Not sure where to go from here. I wish there was a way of completely by-passing all the emissions system and focus on the basics. Since the truck is running I am not sure a local mechanic could do a lot for it without costing me more than the truck is worth.
87 D-150 carburetor 318 engine.

 

did you hook up the esa on the computer? from what i have heard, the older trucks with the electrical system your truck has can be a real pain to keep running good.

 

You mean the vacuum right? yes I did. Could this be a problem with the pick-up coil even though I changed it and gapped it to the best of my ability. or does it sound more like a carburetor/vacuum thing?

 

I hope you didn't use a steel feeler gauge when you gaped the pick-up coil. You need to use a brass feeler gauge.

 

Used brass, but just out of curiosity, what would happen if you used steel or if a screwdriver accidentally touched the coil?

 

Inquiring minds think alike. I asked that very question but could not confirm the answer I got, but here it is. The pick-up coil is a magnetized device and could loose its magnetic properties if a steel feeler gauge is used.