Run a computer diagnostic scan to see what you can find. You'll be able to borrow, rent or buy an OBD code scanner from most auto parts retailers in your area.
If that doesn't show anything, try a compression test. If the compression test is good, just replace the plugs, rotor, cap and wires.
Could be in need of a tune up Could have a vacuum leak
The 1998 Blazer could have several problems causing rough idle. Check the air filter, fuel pressure, and EGR valve for a clog to look for the problem.
You could have the firing order messed up.
sounds like a vacuum leak
Could be in need of a tune up.
A roughneck or a ruffian
Also when you try to give the car more gas. It starts to run very rough.
Check the motor mounts.
adjust your idle...the idle screw needs to be pulled left.
Estimation enables you to obtain a rough answer using only mental maths. An approximate answer can sometimes be sufficient.
you have 2 live Boston and audition when a new season starts
rough.