I have a 2001 V6 s-10 blazer 4.3 Ltd and I believe I have a vacuum leak and misfire in one cylinder! How and what do I use to check for these problems and how to fix them

 

If you have a scan tool, or can "borrow" or "rent" one from a nearby auto parts store, the best test is to set the scan tool up to show the upstream O2 sensor voltages (Bank 1, Sensor 1 and Bank2, Sensor 1). Get a can of "Intake and throttle body cleaner". With the thing idling, and looking at the scan tool, watch what happens when you spray the cleaner into the intake pipe or manifold. First, pull the PCV pipe on the plastic elbow/cap fitting over the throttle body, The sensor voltages should react to that in the "lean" direction (IIRC, higher voltage on these, but it could be the opposite). Then put the straw from the throttle body cleaner in the hole and give it a squirt for a second or so. That should send the graphs off in the "rich" direction, opposite from the reaction when you disconnected the hose.

Reconnect the PVC hose, wait for the O2 sensor voltages to fall into a steady rhythm of waves, and start spraying the cleaner around the gaskets and fittings and sensors on the intake manifold. If you spray cleaner on a leak, you'll get a reaction in the "rich" direction on the O2 sensor(s), disrupting the steady rhythm.

Without a scan tool, bigger leaks will make an audible increase in RPM's when you spray them with cleaner. But the scan tool/O2 sensor is more sensitive.