Okay, this one is a stumper. Decided to go to boards to see if anyone can figure this out. Please read thoroughly the details, we've gone on a few wild goose hunts already. Engine starts, but runs rough, as it appears to be firing only on cylinders 4,6,7,8.

Engine was pulled out of a 2003 Z-28, LS1 w/32K miles on it, fresh out of the car. Excellent condition, and owner is known, so no funny business.

Engine has brand new sensors everywhere, and for 24X reluctor. Changed out oil pump and timing chain to SLP enhanced pol pump and double roller chain and gears. Followed instructions to the letter as for TDC and lining everything up.

Inspected engine while oil pan and front cover was off, everything was clean, no bad marks on cylinder walls or anything. Everything re-installed according to Chevy instructions (I've built numerous bikes, off road machines, and do my own work on my street vehicles, so I'm careful)

Computer's a MEFI 4B, and plug n play harness from CBM; and was sent back for checking last week, everything about harness and computer passed.

Injectors were cleaned and balanced professionally, and just pulled them all to make sure none were stuck, all are good.

Checked all wiring, voltage, everything is in correct place and working. Coils are brand new as well, all are working.

Fuel is pumping at 55psig, cam and crank sensor are in correct spots. Unplugging MAP has no change.

So we are stumped..any ideas? Possible to have gotten timing off anyhow?

 

There's a forum for this kind of issue[s]........

 

There's your problem...your engine does not exist. You'll need to get an engine from a car that actually exists and go from there.

 

If you can, I would throw on the old cam and crank sensors. Also check that everything is okay with the coilpacks - did you switch sides by mistake?

https://ls1tech.com/forums/generatio...ck-wiring.html

 

Might want to go old fashion and break out the timing light to verify timing is in the ball park.

 

You might try switching the coil packs from the firing cylinders to the non firing cylinders and see if the problem is reversed, and do the same for your fuel injectors.