i bought a 91 pickup a couple of months ago, it had a really bad misfire. i replaced the spark plugs, and noticed the spark plug wires going into the distributor weren’t making complete contact causing an arc to form, melting the distributor cap slightly(i’m planning on replacing the cap and wires soon) replacing the spark plugs and adjusting the wires seemed to get rid of the constant misfire, but it idles very rough at every other stoplight when it gets to temp(assuming it’s at temp the gauge doesn’t work) but the next stoplight it won’t idle weird at all. sometimes it’ll idle so rough that it’ll actually stall at that light, and i’ve experienced it dying while driving. it will immediately turn back over, and run fine.
it’s base model, but i believe it has a dlx intake on it, and there’s a literal stick blocking where the power steering vacuum line would be. i don’t exactly know if that’s really relevant to the idle problem, but thought i’d mention it.