Hey y'all

I have a new to me 1990 MM with the 3.0L V6. It currently has a misfire that I'm trying to diag. User xboxrox gave me some direction over on my introduction post, but I wanted to move the discussion over to the proper place in it's own thread. Since my original post I've done some troubleshooting and discovered a few things:

  • The misfire is on cylinder 3 (middle cylinder of passenger-side)
  • The misfire is specific to cylinder 3. swapping plugs and plug wires around does not cause it to move.
  • The coil tested good (1.0 Ohm on primary and 12.3K Ohm on secondary)

As part of my troubleshooting I also pulled the plug from cylinder three and laid it on the metal intake manifold and then turned the engine over. I observed a nice bright spark. This leads me to believe that the ignition system is working properly. (unfortunately. Was really hoping for an easy fix here)
My next suspect area is ignition timing, but there is where my lack of automotive repair knowledge starts to show. Can improper ignition timing cause a dead misfire on a single cylinder? My hunch is that this is not the case. I believe that if the issue were ignition timing there would also be a misfire on the other cylinder that fires with 3 (6 in this case) but 3 is the only cylinder that is not firing. All others appear to be firing correctly. I tested this by starting the engine and then pulling the plug wires from the dist cap one by one. I observed a marked change in engine performance as each wire was unplugged in turn. The only one that didn't cause a change when pulled was of course cylinder 3. If my hunch there is correct the next area I would logically look would be fuel delivery. Again since it's only one cylinder misfiring my first suspicion would be the fuel injector. This is where I'm stuck. The injectors appear like they might well be the OGs or quite old ones at the very least. I have no idea how to test them and it looks like pulling the intake would be necessary to even get to them. Most of the plastics are very brittle under the hood and I want to disturb as little as possible.

Tell me what you think!

Thanks,
OR3X