[Jacfourteen]

I used to frequent the 67-72 forum, but haven't been active for a few years. I will apologize in advance this will be a long one... I bought a 2002 Z71 suburban a few days ago that has me stumped. The seller was upfront that it had issues and as such I got it for a good deal. It starts and runs good, has a slight misfire at idle but drives great once moving. Only code showing is P0300-multiple random misfires. He said it was initially running very rough and he changed several parts trying to fix it including fresh oil, all 4 cats, oxygen sensor B2S1, plugs and wires, and intake gaskets. He said that made it run much better, but still getting P0300. He said he took it to a mechanic and they weren't able to diagnose the problem but said the majority of the misfires were on cyl 1 & 8 and the compression was good. Vehicle looks like it was used as a construction rig (dents, dings, trunk had sawdust, mortar, paint) but seems like mechanically it was well taken care of, I have the invoice for new trans less than 2 years ago, good tires, all new brakes/rotors, etc. My first thought was ground issue since I know this generation has issues with ground points, or injectors. i brought it home and ran some injector cleaner through it with no change, checked all the plugs were plugged in and not corroded, swapped some coil packs, pulled plugs and verified gap, checked compression (all cyl 135-145 psi) and no change, if I clear codes p0301 usually pops up within a minute, then changes to p0300 confirming cyl 1 is the worst misfire. I hooked up my timing light to each spark plug wire and what i found is #1 is firing less than half the time, #3,5,7 are firing about 75% of the time, #2,4,6 are firing 100% of the time, #8 is firing about 75% of the time. all the coil packs seem to be getting solid ground, hot, and reference voltage, but I'm not sure how to check the trigger pulse from the ecm. At the moment all I have is a test light (my multi meters are at a job site in the mountains with a foot or 2 of snow...). I have tried attaching the test light to the trigger wire attached to hot or ground and it doesn't flash at all. I've searched everywhere on the internet but havent found if the trigger pulse is 5V or 12V and thought it might be too fast of a pulse to work with an incandescent bulb. So first question is how do you test the coil trigger pulse/signal? Second question is if the trigger pulse is erratic what would cause that? ECM? If I need a multimeter I can go get a cheapy from harbor freight. I've started digging through the main harness and grounds looking for loose connections and I'm going to keep looking into that, but any other suggestions/help would be greatly appreciated!