Ignition Timing

[Nicka619]

Hello, ive been registered to nico for quiet some time, but never actually posted
I own a 91 240sx, ive had her for bout 3 years now, but was never running. Now i recently got her running!!! Rebuild the motor =D Had to replace the fuel pump from sitting so long, but now i am having idle issues. My motor is very shaky and doesnt remain stable. Ive recently replaced parts that were bad already, including the MAF, knock sensor. Today i cleaned out my idle air control since i didnt when i had the motor out, just to see if it helped.......no success O.o
Now, to get to the problem i am having. Every time i go to do the ignition timing, i can get it to time right on to 20 degrees. But when i hook up a scanner to the car and made sure everything was right, i noticed the computer was reading the ignition timing as 0. Strange right? Is this supposed to read at 0 or at 20? I have no idea where the car gets the reading from and if that part is bad or what? Does anyone know any problem similar to this? I was guessing the distributor reads the ignition timing and can be bad. I did get this dizzy from the junkyard too O.o
Any advice at all? All is appreciated. Thanks! =)

[vancouverbc]

I'm not sure. I think the timing light and computer should be in sync re timing. I think you have to disconnect tps and set idle to 650 which puts computer in timing mode. The computer then memorizes that as 20. Once the computer has 20 benchmark it somehow keeps track of any deviation from 20. I do know that the computer is blind about mechanical timing. you have to tell it where the 20 is. i assume you you didnt go into timing mode.

[Nicka619]

I did disconnect the TPS but i actually did it while the engine was running
will that make a difference if i didnt turn the engine off and do it?

[ShouldaHadaV8]

Im having a very similar problem with my swap. i was confused because everytime i hit the gas it would bog and try to die, when a fellow nico member ran a consult cable and used ECU Talk it showed that my ignition timing was dropping to zero.
so i tried to adjust idle with the tps unhooked, tested the maf sensor, and replaced the ecu with a known working one.according to ECU Talk it is 20 BTDC, its idling at 750, but when i hit the gas ignition timing DROPS WAAAAAAYYYYYY DOWN.
My IACV screw doesn't have any effect that i noticed but maybe i haven't put it in "timing mode" yet ,but im pretty sure it has hit lower than 650 when it boggs and i have tried to adjust it plenty of times ,ANY ADVICE??????? this could be a good reason to start a tutorial on ignition timing.