2006 5.7 Vortec PO300 troubleshooting.

[In-Tech]

Hiya,
I can't remember if the vans still had a distributor or if they were coil near plug.
If distributor/wires they have the firing order wrong(probably old sbc), the new stuff is LS1 firing order.

Ignition Firing Order For Misfire Detection

Sequence Cylinder #
7th 4
8th 3
1st 1
2nd 8
3rd 7
4th 2
5th 6
6th 5

Well shoot, I just looked up a 2003 Express van 5.7L and it still uses the standard firing order(18436572) vs the LS1 firing order(18726543). Either way, if it is using the "crab cap" cam sensor distributor, it's very easy to have wires mixed up, you have to pay close attention to the terminal vs wire and not just location like the old days.

[nevinsb]

Coil near plug (No distributor). It's basically an LS motor with a cast iron block.