Ls swap #2 & #4 cylinders won't fire at an idle
 

Swapped a 2002 5.3l into my 1970 c10
And 2 cylinders won't fire at an idle.
I have good compression and running compression.
Good fuel pressure. Have spark at the plugs.
I've moved the coil from side to side still same 2 cylinders don't fire. Move injectors around still same to hole are died. Tryed new o2 sensors no change. New maf sensor still same two died holes. Changed the computer same thing. Any help going out of stuff to try or change. It's always #2 &#4 cylinders. Thanks

If you've swapped injectors and the problem did not move then your next test will be to check for injector pulse at those injectors with a noid light. Sounds to me like you either have a couple injector grounds missing or they aren't getting signal from the pcm.

Checked with the noid light and that checked out
Good. Thanks anything else

Doesn't really make sense if you are getting injector pulse signal, you've moved injectors around away from those cylinders and have compression across all cylinders.

I have two ideas:
How about vacuum leak(s) at those two cylinders?
Have you pulled those two spark plugs? Perhaps you've got fouled plugs there?

I've changed plug and moved them side to side also.
I'll check for vacuum leaks now.
Thanks

This doesn't make any sense at all. You said you have spark and now you have injector pulse as well. Fuel, spark and compression is all it takes. What about this harness? Is it possible you have #2 and #4 injector wires swapped so they aren't firing at the correct time?

Good thought.

Or maybe #2 and #4 coil outputs are swapped at the PCM? So they aren't timed right? Can you check timing with a timing light on those two? Firing order and some math will tell you what the offset should be from cylinder #1.

Have traced the injectors wire back and they are in the right pin spot. Coils next

Valve springs

Have you checked valve springs?

New springs

Do these cylinders fire off idle and above? How have you determined these
two are not firing?
How is oil pressure? maybe collapsing lifters on those cylinders

Also did u hear engine running in donor vehicle?
How many miles on it?
IN gear or neutral?

They are stone cold to the touch at an idle . They build heat when Rev up but still not as hot as the other 6..
No did hear it got for a freind that heard it run. Oil
presure is good.

Thoughts on cam or crank sensors?

i didnt see plug wires on that checklist, it's an easy test if you didnt already

Sorry forgot new plug wires and have moved them for side to side too.
Thanks anything else

is it throwing any codes?

No codes either

Did you check actual spark check timing of the two cylinders? Maybe the coil trigger wires are flip flopped from the PCM?

Doug