Asking about two separate engine problems in one posting is bound to get folks confused about what's been done with which engine.
My ‘93 350 always had a slight misfire but nothing too bad I couldn’t drive it. Just yesterday drove it to my buddies place ran fine and then several hours later went to start it but it just cranked. It’s getting fuel and all the plugs and wires are good. Finally it started but ran extremely rough could hardly drive it ten feet off the driveway.
Constant slight misfire reminds me of my '88 K1500 5.7L. Failed magnet in the distributor by the pickup coil.
What is the fuel pressure when priming, and when running?
How old are all the usual "tune-up" parts and procedures? Base timing checked? Timing advance checked? Cap, rotor, plug wires, spark plugs? PCV and EGR systems verified? Will the spark jump a spark-tester gap calibrated for HEI?
Connect a scan tool, verify EVERY sensor and computer output.
Funny thing is my 92 305 did the same thing but it would always run rough and it only bit the bullet while I was actually driving it. Just wondering where to start troubleshooting these things. The 305 has been completely gone over. New plugs, wires, distributer, injectors, air filter, oil change, new battery, and just about every sensor possibly related to the issue is replaced. The 305 always ran really bad off and on and when it finally caved I wasn’t very surprised.
What is the fuel pressure when priming, and when running?
How old are all the usual "tune-up" parts and procedures? Base timing checked? Timing advance checked? PCV and EGR systems verified? Will the spark jump a spark-tester gap calibrated for HEI?
Connect a scan tool, verify EVERY sensor and computer output. "Replaced" doesn't mean they're good, and replacing the part doesn't fix a broken/corroded wire harness connecting the sensor to the computer.
The 350 however ran great
The 350 ran great, or it always had a slight misfire?
