Just to put a bow on the initial complaint, and then follow-up with one of the suggestions (for which maybe I should start a new thread?).....
I followed the suggestions to adjust the idle mixture & speed so that the truck would run when the vacuum port on the fuel manifold was plugged off. This greatly improved my original problem of the truck lurching or chugging at slow speeds, such as when backing down a long driveway. I could either endure the lurch and have my neck snapped (and scare the buhjeezus out of my grandson who was riding with me), or I could feather the clutch to make it smooth, but I'm pretty sure that's hard on a clutch. Anyway, problem solved, and thank you guys.
However, the truck then ran and idled rougher in general. I decided to change my spark plugs because they were fouled, I presume from my idle mixture having previously been set too rich or giving too much fuel. While I had the plugs out, I checked my compression (irrelevant, another topic, not good), and I gave the plug electrodes a gentle cleaning with diesel fuel and a soft wire brush. I put them back in, and the truck ran great! Amazing what a clean or new set of plugs will do.
Now for the new, but related topic. Some of you suggested I check my timing. Never done that before, so I read the shop manual (in addition to being aware of all the discussions here). My "octane selector" (page 6-19 of the shop manual), is currently set at 8 deg retarded, whereas the manual specifies "5 deg before top center" (p 12-26), and "5 deg BUDC" (p 12-41).
Q1: Does 8 deg retarded seem way wrong?
Q2: How does 5 deg BTDC relate to the "octane selector". Is that 5 deg advanced? If so, my truck is 13 deg away from that (+5 vs -8) on a 20 deg scale. Yikes!
Can somebody advise on these two questions? Should I start another thread?
Thanks!
