I have a 99' Blazer that I have been having an issue where the truck feels like it's misfiring but not a complete misfire. I would assume you can easily tell on a V6 if there is a misfire. Anyways when I'm accelerating the truck seems to "misfire" randomly. You can feel it, like a misfire but not as severe. I have done the plugs, wires, cap and rotor and awhile back I did the intake manifold gasket and I also did the Fuel pump, filter and spider injector (Upgraded to the MPFI unit) to solve a hard starting problem. Now I have a random starting problem again and what feels like a lack of power when driving plus I am getting like 200 miles to a tank which is pretty bad. I'm starting to think it might be the spider injector assembly as they cause all of my problems when they go bad. Plus I bought the "Standard Products" brand; the offbrand and that could have bit me in the ***.... The missfire could be an injector or two in the spider not firing correctly? Fuel pressure is good so don't worry about that.

Anything under 50% throttle just doesn't accelerate worth a darn. Only when the truck is cold does it run ok and drive semi-normal, when it warms up I start to feel bumps in the idle and the "missfire I have mentioned"

I also just changed the MAF due to a stored code.

Any ideas? Its REALLY annoying!

 

Unplug the MAP sensor see if it still does it, if so, get a new one. An MAP sensor is to the left of the spider injector plug and has three wires.

 

Since you did not mention it, I'm assuming no warning codes?