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Hello, everyone. Been a long time reader of this great forum as well as the other Chevy truck forums GMT400.com, fullsizechevy.com) , but this is my first time posting. A lot of knowledge here so I am sure someone has some idea what is going on with my truck.

I have a '94 GMC Sierra 1500 2wd 4.3 5 speed. The truck has been running fine until the other day I went out in the morning to start it up and it would not stay running without applying throttle and barely has enough power to move. I have to rev the heck out of it and let the clutch out very slow just to get it going. I have replaced the fuel filter and tested fuel pressure (12-13) psi. Also, I put a spark tester on each wire between the wire and plug and get spark on all cylinders. Once I get it moving, if I give it more than half throttle, it starts surging (i think that's the word for it, it feels almost like it's losing all power for a second or two then comes back for a second or two then back to no power. Kind of like the key is being turned off and on repeatedly or like going from full throttle to no throttle) between 1500-3000 RPM. Above 3000 RPM (when I can actually get it the RPMs that high in gear) the roughness goes away slightly but it's still very noticeable and feels like I'm dragging a house and the tach jumps all over. I can get the engine to rev up all the way to redline when it's in neutral or with the clutch in, but it is still very rough. I had a friend come over and was playing with the vac lines while I was in the cab giving it enough throttle so it would stay running. After he took the lines off and reconnected them it ran slightly better for a while until I shut it off. When I started it back up it's every bit as bad as it was before. The check engine light is not on while running, but it does come on when the key is first turned to on so I know the bulb is good. If anyone has any idea what could be causing this issue I'd be very grateful if you could shed some light on the situation for me. If you need any more info from me let me know. I am home all day right now since I can't work without my truck, so I will be glued to the forum. I live less than 1/4 mile from Autozone so I can rent tools if need be. I have had this truck for around 7 years and never given me any trouble until this. I'm really puzzled because I drove it home one night and it was fine, then when I started it the next morning it was like this. :banghead: I have searched and tried some of the suggestions (fuel filter, check fuel pressure, air filter, spark check), but I don't see anyone with the same symptoms as I have. Sorry in advance if this has been answered and I missed something. I also posted this over at GMT400.com and fullsizechevy.com as I am desperate for help. Thank you for reading,

Mike
 
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