Just swapped the h22a1 w/ p13 in my 94 accord lx. I get terrible gas mileage, blow black smoke from exhaust, and it stutters alot from 1-4500rpm and a little from 4500 to redline. Vtec doesnt kick in. Anybody know what could cause this problem?

 

Have you checked the fuel pressure or anything? Get a VAFC and dyno it....

 

If no Vtec - check your oil level first. then check the Vtec solenoid - is it hooked up to the P13? How about the knock sensor? Hooked up?

Any CEL? Blowing black smoke to me indicates your are running rich. Did you replace the O2 sensor while swapping engines?

Did you change plugs, cap, rotor, igintion wires?
Just some basic stuff to check before you go any further.