Misfire getting worse

[sm41]

Hey guys! I finally got my '86 on the road a couple weeks ago. I ended up pulling all the wiring back apart and cleaned everything up nice, and it fired right up! Car ran amazing for about a week, then started misfiring a little bit. Ever since then, it's gotten progressively worse. I thought maybe I was crossfiring 1/3 and/or 5/6, so I rerouted the plug wires. Car ran perfect again for about ten minutes, then started bucking harder than ever. Now it's misfiring randomly and fairly often, at least once every few seconds. Occasionally it'll string a few together, fire again a couple times, then die. Sometimes ("sometimes" being the key word) mashing the throttle will clear it up, but it's always back as soon as I let off the gas.

What has been done recently:
Salt and pepper 10-pins cleaned up. Continuity checked through all wires in the harnesses. Grounds checked.
Double and triple checked the timing. I believe the balancer is accurate. Set at 14* on ethanol-free 93 octane.
Changed the fuel filter/added injector cleaner.
Rebuilt the distributor with a new PIP and TFI module a couple months ago.
New IAC, which cleared up a hanging idle issue I was having.
New plugs. No change.
Regapped them to .052 (they were pregapped to something like .040). No difference.
New plug wires (one of the wires had a crack in the insulation). No appreciable difference.
Did the nighttime wireset check. Didn't see any shorts/arcing, even when it was obviously misfiring.
New ignition coil. Same story, no change.
Injectors all seem to function. When I spin the distributor by hand (out of then engine), I can hear them all clicking.

Only codes that showed up had to do with various pieces of smog equipment being deleted (car has no smog pump, EGR, cats). Anybody have an idea what it could be, and is there anything else I can do to check other buying a crapload of noid lights and spark plug testers?

[AlamoGT]

distributor cap have a crack? Rotor inside look clean? Track vacuum lines to look for leaks?

[sm41]

I'll double check the cap. I don't remember any splits though. There was a bit of corrosion on the contacts for the cap and rotor button, but I scrubbed it with some steel wool. When I rebuilt the distributor and re-sensored it, I cleaned everything out pretty well.

I'l check the lines, but there aren't too many. Just the line to the charcoal canister, the PCV, and the line to the vacuum tree. Everything else is capped off.

[cb650]

How clean is the tank?

[sm41]

When the previous owner took it off the road, he emptied the gas tank. Like, took it out and dumped the gas, then reinstalled. Haven't looked in there myself, but I don't doubt it. I've changed the fuel filter about six months ago when I was trying to get it running (it was very clogged), and again yesterday. This filter looked pretty clean and flowed well. Also, it didn't run any different with the tank full or empty.

[sm41]

Bought a new cap and rotor for gits and shiggles. I must have knocked the old one out of spec when I cleaned the contacts, because it runs perfect now.

[grabbergreen84]

Checked the fuel pressure?

[84GT350CONV]

When you cleaned your distributor cap contacts with steel wool fine pieces left in there might have caused arcing. After using steel wool on different things and blowing it out with compressed air I would still find traces of it on things. Plus it magnetizes itself and sticks to metal parts that way. Next time use fine sandpaper. Glad you got it fixed though.

[sm41]

Checked the fuel pressure?

All good at 40 lbs. I think we're good now.

And I'll keep that in mind 84GT. Thanks.

[JACook]

Good you got it working. Just for grins, take a close look at the rotor. I've seen them crack around
where they go on the shaft, which then allows a very convenient path to ground.

[AlamoGT]

Glad you got it up and running again. Thought it was worth a shot telling you that as it happened to me once with a brand new cap.