1991 LS w/B18b1

[91InTeGRaLS00']

Got 1991 LS with a 2000 LS ALL motor.
Tranny - b18a1 with XTD Stage 2 clutch and 8.5lbs Flywheel
Lighten Crank pulley
Generic Headers with stock Cat and dont kno wat brand mufller

Heres a couple pics of what it looked like before motor was swapped:

Only problem I got is:
the idle is very low at start up wen its cold and even dies out sometimes early mornin. n the check engine light is on.
Any suggestions on how to fix it?

 

[Prozon]

Figure out why the check engine light is on? There's a link about checking the light in the "How To" list in my signature.

You might just need to adjust the idle screw on the throttle body.

 

[91InTeGRaLS00']

Oh yea I forgot to mention that the Idle misfires between 1000 and 2000 rpm wen the engines hot.
I changed the throttle body and the IACV thinking that could be the problem, But no luck.
I tried adjusting the idle but still the same.
The engine line was always on wen we just swapped the motor. Thank for ur help

 

[Prozon]

First thing that comes to mind:
Did you swap the 91's injectors/distributor?

You mentioned that your car now has a 2000 LS motor, which is OBD2, you can't use the injectors and distributor on your car.

 

[91InTeGRaLS00']

the distributor, injectors, and throttle body are 91. Just the motor and intake manifold is 2000.

 

[Prozon]

Did you figure out the check engine code?
Identifying Check Engine Light

And try this link too.
Diagnosing Idle Issues


So it idles low, and wants to die.. and when it warms up it misfires?
Maybe your timing is off. Check that engine code before you do anything though.