I have a 95 with the exact same problem right to the T have replaced almost every sensor last weekend i did the map, and IAC and it ran like a millian bucks for about a 3 1/2 hour road trip but as soon as i filled with gas it started doing it agine and has sense have ran injector cleaner thru it many times hope someone replies with a solution for us gonna look into haveing the injectors cleaned oo and my code says that its running rich on bank 1 but otherwise identical problem

 

mine is starting to point at the transmission. not sure if thats what it is or if thats whats wrong with everyone elses. but seems to me mine is haveing a problem with some kind of solenoid in the trans. got somewhere i could run it good. got it up to 95 mph. (i was impressed with how it did being a really old small suv) on the way home the truck ran excellent, shifted and ran smooth just like it did when i got it. next day it really stuggled and jerked. only did it on the way to the next town in the morning. then it was fine again. i am really starting to hate my truck. i want a ford, lol.

 

i bought a 3 step professional fuel system cleaner for 20 bucks at autozone. sprayed the throttle body out, and let the manifold suck up step 2 as directed and put step 3 in the gas tank as directed. will see if mine stops jerking. currently its really really responsive.

 

I recently threw this code on a new motor. I replaced my injection spider with the updated design. You can get the spider with all new injectors, gaskets, and bracket for about $310 from Rockauto. It really smoothed the motor out. I always felt like the motor had a little miss since 5 years ago. Since I replaced the spider, this thing is golden. The part is a AC Delco, well worth it!

 

I'm glad I don't have a one-of-a-kind problem so maybe someone will have fixed this problem with their blazer and could tell us what to do. I've successfully stopped the misfire as of now. It's a really easy fix. Park the piece of crap. That's what I've done. I have maybe put ten miles on my blazer in the past month. I guess I'm gonna wait till I get the money saved up and take it to a dealership and get it fixed then sell it and go straight toyota. I've given up. I've been told it might be the fuel pump and a guy in town said his suburban did the same thing until he replaced the fuel pump. I don't know...I really don't feel like messing with this anymore. I'm not spending money unless it actually fixes this crapper.

 

My 2001 Blazer had the same missfire problem. I changed everything that you did (plugs, wires, dist cap, rotor, ICM, etc) with no luck. It turned out that my intake manifold gasket, which is a common problem among 4.3's, had failed severely allowing coolant to get inside my cylinder heads.This in turn, rusted 3 ofmy exhuast valves so bad thatat low speeds/acceleration, I had horrible missfires. After a complete valve job on both heads ($99 at O'Reilly's Machine Shop) my missfires are gone and no troubles since.

Hope this helps! Good luck.

 

when diagnosing a misfire it is helpful to do a compresion tes on the engine when it is hot. everything was replaced on mine from injection spiders to fuel pumps to igntion coils etc. turns out that 95 model years have bronze guides in the heads and they were worn so bad that the valves wouldnt seat and in turn cause a miss. and it didnt show up untill i sucked a can of seafoam thru the brake booster hose. so before throwing parts do a compresion test fix any other codes po171 etc. a bank running rich will have a rich miss. same with a lean cylinder it will have a lean miss.

 

I have same proplem we all seem to have. replaced cap ,rotor,wires and plugs. same problem. have not checked compression or manifold gasket yet. But my mpg has gone from 15 to 10.do you think that points to the spider mfi being the culprit?

 

A couple things to check. I have a 98 Blazer that had the same problem soon after I bought it. I went around changing and fixing a lot of stuff, and found out it was my spark plugs. The GM 4.3 V6 does NOT like regular resistor plugs. Platinum only on these engines, as in AC Delco Single Platinums. I did also replace the injector spider assembly, and it cost me less than 200 bucks or so when I ordered from GMPartsDirect.com. You have to know the right part number though. The new injector system gets rid of those crappy poppet valves, and replaces them with real injectors at the intake, rather than at the connector assembly. You also get a new fuel regulator, bracket, and gasket with the kit. I'll see if I can find the part number for it...

 

I had the same misfire at highway/cruse speeds. Mine turned out to be a bad distributor gear. The gear was half gone, each tooth was razor sharp on the end! Replaced the distributor and no misfire.