I put my B16a into my 91 rex dx and now the vtec isnt opening up. what the hell can it be??

Here the following i have done:

1 Checked the computer in another car and vtec engaged.
2 swapped vtec solenoids with a working one.
3 tried a different distributor
4 tripple checked the wiring to the ecu


i am using a pw0 computer


the car is OBD0

 

You said you checked the wiring which probably means that this isn't the problem but is your speedometer hooked up? Vtec needs a speedo signal to the ecu and a certain speed reading to engage. Just a thought.

 

my speedo is working but the weird thing is is that sometimes it only lets the engine rev up to 7200
and i only checked the wires that on the ecu not all the way up to the engine

 

The rev thing is almost certainly your stock tach losing revs as it reads higher and higher. Mine never makes it to 8200rpm, I almost always hit fuel cut off at 7500 on my stock tach, but if I watch it I can see it hesitate sometimes at certain rpms even though I can hear the engine continue to climb. The stock tach is not very precise. Don't know about your vtec however it might be that your ecu is in limp somehow and you actually aren't revving high enough and the limp mode is why vtec isn't engaging. Or maybe your vtec solonoid is shot. I'm not really an expert on this however so I can't help you more than that.