I have a question on a 1993 GMC C K Series 4X 7.4L Engine

I checked for a vacuum leak under the TBI Unit and the Intake Manifold and no signs of any leaks. As far as the Backfiring goes I'm assuming u want me to pull each plug one at a time because it's possible that a Intake Valve in one of the cylinders may be sticking? Because as far as the Ignition System goes, I checked the position of the Rotor in the Distributor with # 1 Cylinder at TDC on the compression stroke and the Rotor was pointing to the #1 Plug so that was good plus I set the timing while running to 4 degrees BTDC and it was running good at that point, so with the ignition set properly their is no way the timing could be off unless the Timing Chain is worn and possibly jumped a few teeth or like I said one of the valves is sticking! Also on the Ignition Module I replaced in the distributor I did put dielectric compound on the bottom of the module because it said on the box it came in that if u didn't it could damage the module due to heat build up! I'm actually a Auto Technician myself but only on Ford vehicles have I been trained on and was fully Certified! I went to school at UTI for a couple of years also, but The older Chevy/GMC Vehicles I'm not to familiar with so I thought I would ask someone who has had experience on this particular vehicle! The concept of things are the same with any vehicle but their are some differences on the older vehicles to the newer vehicles plus each Manufacturers vehicles can be set up differently and without Wiring Diagrams and other Diagnostics to help u pinpoint the problem makes things difficult.

True they do work the same Lol! Just might have a different layout is all! Yeah with the new Distributor Cap I didn't see any tracing or anything unusual. Oh yeah your right, a worn Camshaft lobe could cause that same problem! So Chevys are natorius for their push rods being pushed through the Rocker Arms huh? I guess if I can find which cylinder is misfiring I can do a little investigating and narrow it down to the cause of the problem! As many miles that are on this Engine, I wouldn't be a bit surprised that it's a Mechanical concern of some sort for the Backfiring. But as for the Fuel Injectors not spraying fuel, what could be the cause of that problem if their isn't a vacuum leak? I was thinking it could only be 3 things that I could think of, either a defective ECM, defective fuel injectors or fuel injector assembly or the Fuel Pump could be going bad. Could the Sensor that Monitors the Vacuum to the TBI also cause that issue if it's defective? What is that Sensor called?

Yeah OBD 1 is out of my ball park also! Lol! I got to use OBD 1 Scan Tools when I went to UTI but haven't touched one since! I've only been Auto Teching for 6 years and Everything I have dealt with is OBD 2. OBD 1 is pretty much almost obsolete anymore! The dealership I used to work for threw most of their OBD 1 tools and diagnostics in the back room because most of the stuff we dealt with was OBD 2, and I have a code reader of my own for OBD 2 but it's no use for me on this truck I'm working on! The company I'm working for now just has me repairing their vehicles on the job site and most of them are Chevy vehicles some are older and some are newer! They do have a few Dodge Cummins trucks also! But without the proper diagnostics, it's pretty much a guessing game! But with what knowledge I have and the help I'm getting from u, maybe I can get this vehicle figured out! I've almost been Tempted to replace the ECM because won't it come with a new Prom also? At this point given my situation would u just say replace the ECM and take a chance? These trucks this company uses is off road kind of like a Construction Company and the area they drive in is bad! These trucks get the hell beat out of them so by the looks of it, these vehicles have been worked on a lot!