When I first got my '87 it had a horrible surging idle (5 speed truck.) It does have EGR and the problem eventually just went away? Was really weird. The only thing I can attribute it to was bad fuel/partially failed fuel pump/etc. It sat for 10+ years and did not like running off the old fuel. I cleaned out the tank and replaced the pump, sending unit, and filter but I think I left the high pressure pump in place since it worked. I had a horrible surging idle for quite a while and it eventually just cleared up.
Not that any of that helps you, just my experience. This is certainly fixable, just a matter of time and narrowing down the cause.
Glad to see that your EGR valve isn't stuck. Exhaust gas coming up through the tube is normal. Have you tried applying vacuum to the vacuum port on the EGR valve while the truck is idling? I think you should be able to watch and see how it moves and it should immediately affect how the engine runs. Can you verify that it closes completely as it should?
It's helpful to hear stories of people overcoming their truck's surging idle. That's funny your issue just went away. The same thing kind of happened to my '89 Econoline. It had this same damn issue and it drove me nuts sometimes but it would go away and return and I now cant remember the last time it did it. When we got this ranger and it did the same thing I thought well shit it must be a ford quirk. I even asked some mechanics if they've noticed if a lot of old fords they work on have surging idles and they said definitely.
I replaced the high pressure fuel pump and fuel filter when I first got the truck because it was dying randomly and I couldn't hear the pump prime when Id turn the key at times. New fuel pump didnt fix the issue and I later learned the issue was a faulty ignition switch. I havent touched the in-tank pump so I don't know the state of that one but my fuel pressure is within spec so I'm doubtful its a fuel issue. This truck's my daily driver so its constantly getting fresh fuel.
This truck also sat for years before the previous owner purchased it from a neighbor. The truck was a father son project. It had a blown head gasket so they took the engine apart, put in new valves, new heads and gaskets, water pump, radiator, timing chain, injectors, egr valve, catalytic converters, brakes, brake booster, master cylinder, shocks, fuel pressure regulator, IAC, TPS, MAP, TFI, O2 sensor, belts, hoses, tires, manual locking hubs they went all out and the son got bored with it so the dad sold it to my girlfriend and I for $2k. He was kind of relieved to be done with it haha. I don't have it in my notes that they replaced the in tank pump or cleaned the tank so I guess I don't really know whats going on in there. I'd assume with all the work they did they know they'd have to do something about the tank on a truck thats been sitting.
I checked the EGR by blowing through one hole and plugging another (cant remember which combo it was now) and without vacuum applied to the vacuum port I couldn't get any air through. When I applied vacuum the valve opened I could then blow air through. Yeah I've also applied vacuum to the EGR with it running and the truck immediately stumbles and If I remember correctly it stalls. This was a test I did in the early days trying to troubleshoot the EGR system.
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