Own 1997 blazer 4wd i am getting ramdom missfires on #4 #6 check engine on codes po300 changed fuel pump plugs wires also when i drive truck when auto trans shifts the truck lacks power or boggs down through the shifting process any ideas mike

 

Sounds like it could be the cam sensor. You might try cleaning the maf sensor, if its reading wrong it will throw off the fuel/air mix.

 

Sorry I ment the crankshaft posistion sensor lol. Also, did you use delco plugs and wires? Other brands can give you random misfrires.

 

Did you have those same symptoms b4 changing all the parts or after? Were the plugs fouled with gas at all?

 

the problem po300 was there before i changed plugs and wires i am going to change out cap and rotor next and clear all the codes the funny thing when the truck shifts it bogs down for a second or two like its starving for gas recently had a garage change the fuel pump and pressure regulator 900 dollars ouch

 

Make sure to use delco, other brands can give you random misfire.

 

Been there before. The first thing I'd do (I didn't do it myself even with 30 years doing mech. work) is to spray starting fluid inside the throtle body. If the problem is strickly a fuel/injector the blazer should start for a few seconds and stop running. Keep in mind my blazer also gradually got to the point where it would not start but, it does briefly when I spray the starting fluid. Had I done this first I would not had changed plugs, wires, timing chain w/cover and the fuel pump that was working. I haven't fixed it yet but, I know it's in the top intake manifold area. The blazer was running just fine before I replaced the transmission and after that job it started with a misfiring issue untill it just didn't start any longer, unless I sprayed starting fluid. Don't go crazy with the starting fluid three bust is enough and do it at least three times. Listen or see if it shortly starts and run normally. If it does, look into the injectors and pressure regulator assembly. I'll be doing this on my blazer but, before I do, I'll change the inline fuel filter. Good luck! I'll consider myself lucky if the injector unit from the old blown motor I bought last year works. P.S. the injector unit is a $400 item and that's if you do the job yourself.