timing, tps or?

[L Tankman]

Hi all, been having a very large idle problem with my vg33e for a while as its been sitting in my yard waiting on me to figure it out. I had it at one point running smoothly but after tearing it down so many times I feel it could be a slew of things. Currently the idle rhythmically surges up and down and is making it impossible to ensure my distributor/cam timing is correct, so here's my questions.

When replacing the TB and setting cam timing, one should turn the engine by hand a few revolutions. During which, are the timing marks supposed to line back up if done correctly?

If my cam and distributor are correct, my next thing to check was the tps. I set it to .5 volts and at WOT turned to 4+ volts, yet when I started the vehicle the volts would jump from the measured voltage to random voltages, is this a bad tps and is it producing my idle issue or is it a byproduct or non related?
May I include that after testing tps, with key on engine off, and throttle at mid range there is a buzzing coming from firewall area on cylinder 1 side.

[ezb57e]

The cam timing marks will not line up again after a few turns. They will eventually after a certain (large) number of turns.
You can set the TPS with the key on, engine off. A bit under .50V is best.
It should be fairly steady with the engine running. If not, check your input voltage and connections. If all that is OK, the TPS may be faulty.
On some cars, there is a solenoid that will buzz when the TPS is off idle, then stop when it is returned to idle.
Also, there may be a "soft idle" switch that needs relearning too. With the TPS disconnected, rev the engine a few times, let idle and reconnect TPS.

[L Tankman]

Thank you for some feedback, I'm going to try that with the tps tomorrow after work.

[L Tankman]

Ok, today I started the pathfinder with the tps disconnected and my oscillating up and down idle was now a much smoother idle and voltage remained steady under half a volt. Soon as I plug the tps back in my bad idle comes back. Bad tps?