The nightmare problem I had with my 93 B2600i ended up being the distributor. I think some of my posts are on this site (unless they got lost with a web site problem or something). In process of trying to get to the bottom of my problem, I got the engine computer refurbished, a new MAF sensor (or was it MAP sensor? - it was a big thing that the intake air goes through), a new ignition module, I cleaned and inspected some of the wires, and maybe a few other things before removing the distributor, which had a cap that looked normal to me, but the distributor itself even I could tell was bad when I removed the whole thing and examined its internals (some internal parts were so delicate they disintegrated upon touch - and I thought 'it's a wonder the truck had run at all'). Once I got to the distributor, pretty much by process of elimination, I was surprised it had not been more difficult to understand the instructions in my Haynes manual about how it needs to be oriented for the timing to be correct. And I bought a timing light gun from HF and checked and/or set my idle speed also at that time.
My nightmare problem defied 2 mechanics who I paid early on to diagnose it, which surprised me and reduced my confidence in them. The engine computer mail-away refurbishment service and MAF sensor were the result of those two diagnoses. Doing those things was putting up a lot of money for such an old truck (though the engine computer refurbishment seemed to help some and that may not all have been my imagination). After those two high-dollar failures ($200-$300 total) I decided to take the time to think about and observe the problem carefully each time it happened, looking for hints, posting and reading the info available on this forum. Somehow I came to believe it was an electrical problem and got around to inspecting the distributor (after months and months if I remember correctly).
Like yours, my main symptom was unpredictable stalls and the engine's failure to start for a while afterward, which became less and less predictable over time. On another vehicle ('97 Chevy Astro) I'd had a plugged fuel filter cause a stall that would clear by waiting a while, but that wasn't my B2600i's problem. I'd had the engine rebuilt, but the distributor wasn't a part that was replaced at the time and the problem happened a few years later (at about 220,000 miles, 25k or so after the rebuild). That problem was maybe 5 years ago and I'm happy to report that my B2600i is still running well and that I'm glad I didn't give up on it, though pressure built to do so as it was parked a lot and, when used - which was necessary to obtain further clues - sometimes caused trips to be disrupted, resulting in waiting until it would start again or leaving it and getting another ride or walking. It became enough of a frustration that before it was fixed some family members began referring to it as junk, having simplistically concluded that it had a problem that was just impossible to solve. Eventually my persistence was vindicated and I hope you have a similarly good result!
Last edited by OldMazzies; 05-15-2018 at 01:18 AM.