Random misfire (code P0300)
 

Hi, I'm new to the forum...trying to get my son's blazer up and running again. Last summer before he left for a job in NC (from MO) we replaced the battery and alternator twice (faulty replacements from O'reilly Auto), as well as a fuel pump. A few months later, he could only get it started if he "jumped" it or hooked up the charger/booster, despite a good battery and alternator.

Fast forward to now. I replaced:

• ignition coil
• distributor cap and rotor
• plugs and wires

Still wouldn't start easily, usually without help. Checked fuel pressure, it was running highs 40s. Changed fuel pump yesterday with OEM this time, BOOM! Started right up. However, I now have the random misfire happening and it bogs down when trying to accelerate.

I put in Autolite double platinum plugs--not the cheapest, but not the most expensive, either. I double checked the gap and set to 0.06. My suspicion is the plugs; I've since heard from someone that this engine can be "picky" and the iridium plugs are necessary. One way or the other it has to be something I swapped out because the problem didn't exist before the new stuff. If it was a wire, the same cylinder would be consistently misfiring.

Thoughts?

2001 Blazer with 4.3L

These engines are touchy when it comes to secondary ignition parts. Stick with AC Delco plugs, wires, cap rotor. Hundreds of threads on this forum refer to this.

Fuel pump should either be AC Delco or Delphi or there is risk of replacing it again in a few months.