So a bit of an update: I replaced the injectors, fuel pressure regulator, and fuel filter. Still acting up. It starts fine but during even acceleration I can feel it missing, kind of like I'm driving over some small bumps or potholes. Still need to do the tap test on the ecm. Could still be fuel pump too. Will update when I figure it out.

I finally got the car to my local shop and they figured it out. They said one of the spark plug wires was iffy, ie. missing occasionally, but probably not the problem. So they replaced those but the real problem was the torque converter lockup in the transaxle. Once the unit was unplugged the car runs fine. Plug it back in and it runs jenky again. I'll lose a tiny bit of mileage but that saves me a $700 repair. Supposedly this was a common issue and it'* usually just unplugged.

I had always noticed in 3rd that it seemed like something engaged/disengaged depending on throttle, kind of like the vacuum secondaries on an old 4 barrel carb or an extra gear but never knew what it was. You learn something new every day.

Well, disconnecting the harness, only masks the problem.....

With no lockup, that transmission is going to slip, and eventually slip a little more, and increase transmission fluid temp....

Anywhere I can read up more on torque converter lockups? I have a good basic idea how auto transmissions work but this is the first time I've come across one of these. I watched a couple youtube videos and read some forum posts already and there doesn't seem to be a consensus on whether unhooking them caused damage. Our local mechanic seemed to think it wouldn't hurt anything but my mileage but I'm always up for learning more. I should add that as far as fluid temp my car came with an extra transmission cooling radiator, only pushes 160 hp (or did in 89 anyway), and isn't used for towing. I also drive sporadically as I work from home and don't commute more than a few times a year.

I only mention this, because we are talking about almost a 30 year old transmission...yes it does have low mileage, but what has the maintenance been over a 30 year period?

In your case, the tranny, without lockup, will go on possibly for years, or **** the bed tomorrow, now one can predict what will happen......

With out the TCC, that torque converter is not "locked" to the engine....

For example, you are cruising along, and you slightly accelerate......that transmission may slip 25 to 35 rpms.....with no TCC, now we are talking 200-300 rpms, or even more under a harder acceleration....

There are numerous causes for no TCC.....bad/open wire, bad solenoid, plugged filter, sticking valve/ball valve, leak in the actuating fluid circuit, or bad torque converter......