2006 gmc envoy 4.2. Car battery, alternator, and starter test fine. Just had it in for a bad fuel sensor relay. Shortly after I have noticed the car is slowly losing power during the start up. Last I tried it has just enough juice to start the truck. Tried to charge the battery and it didn't help. The battery is about two years old. Any help is greatly appreciated as I can't afford to bring it in.

SOURCE: engine

possibly a plugged catalytic converter?

SOURCE: starter needs to be changed on 2006 monte carlo

It sound to me like the starter solenoid is bad. If you can remove the starter yourself you should be able to repair the problem. You will need to remove the terminal cover from the solenoid(be careful because there are wires connected to the underside of those terminals so do not force it.) If you look at the back of the terminals you will probably see that the inside part of the bolt is burned. loosen the nuts that hold the terminals and rotate them so that the burned sections are to the outside then tighten the nuts back. (not too tight because you can break the plastic) You can test the starter before you put it back in the van (after reassembling the starter itself of course) by connecting a set of jumper cables from the battery to the starter. Negative gets clipped to any good metal tab (usually where the mounting bolts go is a good spot) and the Positive cable goes to the big terminal where you first removed the cable from. touch a screwdriver to the smaller terminal and then touch the screw driver shaft to the + CABLE CLIP (not the terminal because you can damage the threads if it arcs) Be sure to have a good grip on the starter because if it works then it will jump. And keep your fingers out of the hole where the gear (Bendix) is because when you bridge the contacts the Bendix will pop forward and will shred your fingertips.

SOURCE: Changed alternator & battery but car does not charge

make sure all those spots the wire daisy chains too arent corroded and clean and shiny bright, check all your connections and check that theres no corrosion on the bolts or mounting points. other then that you may just have a bad alternator again, autozone parts arent always the best

SOURCE: PUT BAD GAS IN MY CAR AND NOW IT IS GIVING ME

your problem is not in the charging or the starting system yoiu need to drain the gas and put fresh fuel in it, also try to an additive.

SOURCE: 97 cavalier z-22 starter or solenoid problem?

Get your battery tested.