voltage fluctuation and misfire.
 

I’m having problems with the voltage gauge fluctuating between 12 & 14volts changing the alternator hasn’t sorted it. I have also checked the battery to see if it had a dead cell and that according to the battery checker its fine and doesn’t drop a charge, so is there anything else that anyone can recommendthat I check out as the problem only occurs when I have the lights and heater on and the electrical system is under full load.

I have also noticed that within the last couple of daysit has acquired a misfire and every so often the engine management light flashes for a few seconds and then goes out. I’ve changed the plugs and HT leads but the misfire still persists.

Could the misfire and voltage fluctuation be connectedand if so how?

I don't know what year your truck is but at one point they started having the PCM control the voltage regulator. This is a recent thread that may be related. Pay special attention to what Captain Hook had to say.

https://blazerforum.com/forum/2nd-ge...answers-81146/

1997 and older voltage regulators used battery voltage to control the regulator and could not cause the problem you're describing. 1998 and newer uses PWM, (Pulse Width Modulation) from the PCM to control the regulator. The link that spittybays posted explains how to fix it once and for all.

Sorry it's a 1999 LT and thank you for your replies but I managed to sort out both of the problems in one today. The multiplug by the coil just required cleaning and everything now works fine. No misfire and the voltage under load is as it should be.

hi, what exactly is a multiplug by the coil? i would like to inspect this on mine to. please let me know, thanks