timing off?

I have an issue with my 240. It'll die when I'm braking. The rpm will just drop and die down. So I have to keep my foot on both brake and gas. Other times when it doesn't die, the rpm needle rises up a couple hundred rpm and then drops back down. It repeatedly does this otherwie, every once in a while it stay at 900 rpm. Is the timing off and I have to re-align the crank pulley? Or do I have to mess with the iavc? If its the iavc, is it located right in between the motor and intake manifold by the firewall? Right below that piece that bolts onto the intake manifold and connects a hose to the fuel rail? If its that how do I gain access? There's so little room.

I think I've got the issue with the car dying, and it stopped struggling right before the shift point. But sometimes it still will drop to 600rpm and raise up to 800-900 rpm then drop back down. Then other times it'll stay smooth at about 850 rpm. What do I have to do in order for it to idle smoothly at 900-1000 rpm? I was told by a mechanic it should idle at 1000 rpm.

idle air control

Where exactly is it located? I've been trying to find that in the chilton manual but can find it anywhere in that book.

The IAA valve assembly is located on the passenger side of the motor down
below and behind the intake manifold. It's about 8" from the firewall. According to the Nissan shop manual, to adjust the IAA valve, disconnect the throttle sensor harness connector with the motor shut off. Now with the engine idling in neutral, adjust the IAA for an idle speed of 650 RPM. With the motor shut off, reconnect the harness connector. Now with the motor idling, you should have an idle speed of 700 RPM. If you can't get the proper idle speed, the AAC valve may be defective as It's the one that receives signals from the ECU. The AAC bolts on to the IAA.

Also your AIV could be dirty.
Your throttle plate could be dirty causing it to stick.

btw, you should also have 1000+\- rpm at idle is with a/c on