Getting owned by an 87 TBI

[GetItBilly]

Sorry, either I'm totally missing something or I didn't explain what's happening in the video clearly. What I intended was to ask if I can focus on investigating a (hopefully) short list of specific things given the behavior and readings in the video in combination with items I've already done listed in my 1st post, like dist, plugs, wires, timing at 0, etc.

After 1:04 in the video, when the MAP is unplugged, my intention was to show via the vacuum gauge that the engine seems to be mechanically healthy per the classic tests of how the gauge's needle should react under various conditions. By the way, I do see vacuum increase a bit as steady rpms increase, which I believe indicates exhaust is flowing well.

At the start of the video, with the MAP plugged in and feeding the ECM, I intended the video to show, first, that the MAP sensor voltage readings look correct. Second, between :05 and :024, I am not manually blipping the throttle open and closed. I am doing my best to hold the throttle open at roughly 2000 - 2100 RPMs. This is my "stumble and bumble" :). It does the same thing under load in gear. In the video, RPMs are cycling/dropping from ~2100 to ~600-700. I don't think I can do an aggregated knock count with my scanner, but it never reports a knock. Coolant temp is being reported correctly via OBD.

So what I was hoping you could help me learn is what the ECM is trying to do here. I learned it uses RPM and MAP output to set timing. With MAP unplugged, it uses a default fuel map. RPM and MAP readings look correct via OBD scanner.

This is a new-to-me-truck - I have no standard or history to compare how it's running with. Engine might not be stock. When it first got delivered, timing was set at 8 degrees advanced, maybe even a little more. I guess technically it ran better than it does now, but still not really good at all, and idle RPM was so high it was a pretty brave move to actually put it in gear.