Random missfires 2000 blazer with csefi, i replaced the fuel pressure regutator because of hard starts, now it starts but has random missfires, plug wires are correct and did not missfire before changing the regulator.

random misfires are from injector and low fuel pressure problems

Anti theft system failing maybe? Read this link and compare symptoms http://vatspasslockpasskeysecurityhelp.yolasite.com/

Im sure if its fuel causing your misfire but here are the fuel pressure specs depending on which one pertains to yours if your has a TBI Throttle Body Injected the the fuel pressure should be approx.9 to 13 psi if you have Multiport Fuel Injected (MFI) then the pressure should be approx. 41 to 47 psi if its Central Multiport Fuel Injected (CMFI) then the pressure should be approx.58 to 64 if you have Central Sequential Electronic Fuel Injected (CSEFI) then the pressure should be approx. 55 to 61 all these pressures are key on engine off if you start the engine and take a reading then you will have a decrease in reading by about 3 to 10 psi.

first off, just take distributor cap off and check the cap for corrosion and pitting. turn the dist. shaft by hand. if it turns a lot then the gear on bottom of dist, shaft is worn. you can either replace dist. or replace gear on shaft. check all wires and plugs. hard to say, but i would start at distributor to see if it is ok.

Could be plugged fuel filter, faulty fuel pressure regulator (check your pressure) and most probable is a sticky or dirty injector. Do check your timing as well.

cam shaft position sensor or problem ECM and wiring

do you know for sure its the injectors?

Check for cold start injector for proper operation, check for dirty fuel injectors, check for fuiel filter.

my 96 blazer would have random missfires.... sometimes more than one cylinder at a time... there are a few things to try.... 96 vortecs still used distributor caps... but they had such a high intensity spark that they were well noted for frying distributor caps and ignition coils... i would start there... also a few times i had to replace the crankshaft timing sensor.... it could be something as small as a spark plug wire... i would start with the ignition before spending money to check the fuel system

Just to let you Know what you R getting into-I just got rid of My 2000 Blazer (THANK GOD)!!!! If you check out the Recalls and Complaints Online for the 2000 and Up Chevy Blazer you will be Reading for Months!!!! I am Chevy to the BONE and bought this for My Wife-It was GREAT for the first 15000 Miles and then Everything went Haywire! The Seats Broke, Lights quit, Tranny went Twice, Brakes Failed 3 Times, NEVER Ran Right again, Guages quit working, ON and ON and ON. GM will NOT honor these Recalls and Fixing them is REALLY Expensive. Just MY Opinion But, GET RID OF IT WHILE YOU CAN!!!! Took a BIG loss on Mine and Don't Regret it!!!!