Vortec weird engine issue

[White96k1500]

I have a 96 k1500 with the vortec 350 and after its been sitting and I go to drive it for the first 30 seconds or so I can barely get going it has no power it seems to back fire and the more throttle you give it the worse it gets when I first Drive it i can barely go above 1/4 throttle with out it dieing out but once I get a couple hundred feet down the road it's just like a flip of a switch and it suddenly runs perfect and has a little of power,I have already done a new fuel tank,fuel filter,fuel pump

 

[White96k1500]

Can anyone help???

 

[Jay33089]

Can anyone help???

I had the same issue. I had ruled it to be a leaky poppet valve or two on the spider. Mine would only do it after the truck was hot and you turned it off while you went in the store or something. But it was consistent. Got to where I would just leave it running! But it developed a bottom end knock so I ls swapped before I resolved the issue. Not guaranteeing this is your issue but could be a place to start.

 

[White96k1500]

Thanks for the info that's kind of what mine was like,it would happen after I shut it off and started it back up and I had a feeling it could be the spider

 

[lowreese26]

How would one test something like that. I am having the same issue. Thought my fuel pump is going out again. Only when it’s warm and I go somewhere and turn the truck off and start it again fairly soon after.

 

[White96k1500]

Now that I'm paying attention more that's what mine does too I went and got a used spider but I took the whole intake off and didn't even take off the upper intake because if you just try taking the spider out the lines will Crack and you'll have to do it again