have been working on my 97 AWD blazer for 2 weeks trying to find a solution to this problem.

after the vehicle sits for a few hours and it is humid out it misfires on random cylinders.

symtoms:
only happens between 1800 and 3000 rpms
only happens if it is humid/wet
stops after 15 mins of driving
sometimes it seems the throttle is unresponsive

what i have tried:
changed plugs,wires,cap,rotor,coil,vacuum lines
tested tps with oscilloscope
unplugged MAF problem persisted
cleaned injectors
added fuel additives
checked fuel pressure
sometimes i get a p0300 random misfire code but rarely

the more load on the vehicle the worse the misfire is. it will still misfire at 2000 rpms even in neutral

 

could this be a crankshaft position sensor or a distributor?

 

i changed the crankshaft position sensor and the problem still persists. i really love my blazer but this problem is rather annoying.

 

Theory, if you unplugged the MAF sensor and the problem persisted.....did it throw a code for the MAF when you did this? Just saying it would make things worse if it was working right, just a thought. If the computer, for some unknown reason, is using stored data instead of sensor data that could be why it's giving you frits when it is humid out. Another possibility is your O2 sensors. Sometimes when they start to go bad they "hang up" on one voltage reading, making fuel delivery not adequate for what you are trying to do (aka test O2 sensor(s)) Also ohm out your ignition coil, it sounds like your not getting a hot enough spark because, after you drive it a bit it seems better (except under heavy loads)
Your CPS does nothing more then tell your vehicle when to start, usually when cyl 1 is TDC so if it's working your truck will start.

 

after some reading i decided to investigate the ignition control module tho i was told by many people (not in this forum) that it was most likely not the cause. so first i removed the old 1 and cleaned the plug and the module with electric contact cleaner and left it set for 10 mins. then i noticed the thermal compound was hardened up so i cleaned the surfaces with steel wool and applied new compound. fired it up and it ran worse than b4. so i went to autozone and tested the module and it failed. so i replaced the module and boom! problem solved! runs better than it ever has . so if anyone else is having a random misfire code and getting extreme hesitation/misfires almost to the point of engine stalls especially when it rains definitely look into ignition control module replacement. i hope this post helps people who have similar issues. thanks to everyone that helped me out.

 

thanks for the post . im having those same problems pretty much . im going to look in to that for sure