before but thought I'd share this. 6K on a new set of injectors (pensacolas). Slowly been developing some hard knocking at idle in gear. At the same time I've been having problems with a random slow starting crank speed. I've been suspecting a bad ground somewhere. Well I finally found the bad ground (passenger side battery ground cable broken inside the lug) which I promptly fixed. The knocking has gone away. I know there's got to be something to some injector failures and a bad electrical system. Wish we could figure it out. In the meantime it's my belief that keeping the electrical system in top shape is really important on these trucks.

Also, corrosion inside the battery cables , especially the positive cables. Overtime the outer coating on the battery cables develop small cracks from being exposed to heat and cold allowing moisture & road salt to infiltrate the cable causing corrosion on the inside of the battery cable . Usually it is not noticable just looking at the cable. It is a known problem with GM cars & trucks. Probably other vechicles also. Charlie