Cammed LQ4 first start backfires

[tpickrem]

Hey guys,
I finally got to start my LS swapped Chevelle. It's a cammed LQ4 (231/235 at 0.050 and .626/.605 lift) with 243 heads milled 0.020" and ported. Victor Jr intake with a holley 4150 style throttle body and deatschwerks 50lb injectors. The car will start right up but only runs for a few seconds before backfiring out the exhaust (currently open headers) and then it immediately dies. I made a mark at TDC and checked the timing with a light but it doesn't seem to be advancing (even though I have it commanded to 15 degrees to check it). I'm sure the fuel table is off but I'm also wondering about the timing. Why is the light showing no advance? I'll post the tune file and a couple logs from startups and hopefully someone can help me out.
chevelle first start tune 1200rpm.hpt
startup attempt 1.hpl
startup 2.hpl

[tpickrem]

bump

[kevin87turbot]

If it's backfiring out of the exhaust, then it has a ignition issue. It's very possible that one of the ignition coil harnesses is swapped from end to end. If it's on the driver's side, it will cause cylinder 7 to fire when it should be firing cylinder 1, and 5 and 3 will also be swapped. It could also be the passenger side.

[tpickrem]

If it's backfiring out of the exhaust, then it has a ignition issue. It's very possible that one of the ignition coil harnesses is swapped from end to end. If it's on the driver's side, it will cause cylinder 7 to fire when it should be firing cylinder 1, and 5 and 3 will also be swapped. It could also be the passenger side.

Thank sir! This was indeed the problem. How do the harnesses get swapped end to end?

[kevin87turbot]

The mechanic that worked on it must have flipped the harness around. It's an easy mistake to make.