I've had this problem with my 87 B2200 with the Nikki carb. for a couple years now. On a hot day, when I go up a hill, sometimes I would get some misfires. Occasionally it would stop running altogether until it cooled a bit, then it would run pretty good with just a little roughness. The next morning or on a cool day, no problem. I was thinking a fuel problem so I did all the fuel stuff: Replaced fuel filter and old hoses, even rebuilt the carb myself (whew! that wasn't easy) because I couldn't find anyone who would work on it. Got 'er back together and CRAP! Same old problem. The problem however was getting worse lately. Sometimes it would stop running, period. So it stopped running 2 days ago as I pulled into my garage. I thought, hmmm, I'll check the spark.
VOILA! No spark!

So I got the 'ol Haynes manual out and did the resistance checks on the ignition coil and it checked OK. I even opened up the distributor and removed the Igniter (sometimes called the Ignition Module) and checked the resistance on the pickup coil windings - OK. So I figured it had to be the Igniter module. Mazda wanted $315 for one, other stores online wanted $200+. I didn't like that. I found one at Autozone (Duralast brand) for $69. That sounded good to me. I put that sucker in and got major spark up the 'ol Tesla coil! Put 'er all back together and she runs SWEET! For a 20 yr old truck it runs great. I just can't bear to get rid of it for some reason. Hope this helps someone else with an intermittent ignition problem.

 

I also had intermiitent and rough running, replaced both the ignitor and module in my '88 B2200 to fix it.

 

I also had intermiitent and rough running, replaced both the ignitor and module in my '88 B2200 to fix it.