New LM7 swap performance issue

[ducrider123]

Thanks for the add. I’ve read tons of posts and have learn all a lot of stuff, but I’m having a problem with my first engine swap.
I swapped a 2002 5.3 LM7 DBC into a 1983 c10. 140,000 mile engine. All stock. Factory computer VATS deleted by LT1swap. I reworked the harness (first time), Doug Thorly mid length headers, original o2 sensors, knock sensors, air cleaner and box, ep381 fuel pump. 4l60e tranny (unknown condition supposedly good)
The engine starts up and comes down to idle. Revs ok with in park, except it takes a second after throttling up for it to come down to idle. When test driving it to test the transmission it does not have any power. Scanned and there are no codes. The exhaust is two pieces of 16” pipe past the O2 sensors. Also, not sure if related but it shift kinda weird. Coming to a stop it doesn’t go down to first gear.
Any help would be appreciated

 

[Camar068]

When test driving it to test the transmission it does not have any power.d

make sure you don't have your o2 sensor connectors switched up. Mine were and it would run rough until I put my foot in it....then like a scalded dog.

 

[ducrider123]

Do you mean pass on driver and visa versa? Or front and rear? The rears have been deleted and I’m pretty sure they are correct but I will double check. I am checking the fuel pressure when I get the test kit from a friend on Tuesday.

 

[yevgenievich]

It is possible that trans is stuck in limp mode. Will be in 2nd or 3rd gear.

 

[ducrider123]

limp mode is possible. how do I get it out? I don’t have a programmer. I can run it they all the gears manually.

 

[yevgenievich]

Have to go through a diagnostic drive and verify what the transmission actually does.

 

[Camar068]

Do you mean pass on driver and visa versa? Or front and rear? The rears have been deleted and I’m pretty sure they are correct but I will double check. I am checking the fuel pressure when I get the test kit from a friend on Tuesday.

the fronts. Can't remember the color but they were both close. Like one side has purple and the other with a purple w/white stripe. I had mine switched up.