Noise in idle

Can you get a recording of this? Also, what do the RPMs drop down to? More than likely the idle dropping is why it is doing all this as it is too low. So if we fix the idle issue then we will fix all this other stuff.

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

We need to look for a vacuum leak so here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

The idle control is computer controlled so I suspect we have either a mechanical issue or the PCM is malfunctioning. Let's also check for codes and go from there.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Thanks

Hi: The RPMs start a little high at 1,300, and keep this way for a while, then drops at around 710 and the truck starts shaking. The fuel pump pressure is 39 PSI (constant). I have noticed that the truck works better when the fuel tank is full than when it is around 50% or below, but the fuel filter is new. I am suspicious of the coils or the spark plugs; I changed them all one year ago. I noticed that there are some kind of irregular explosions similar as when the is a fault of current. Tomorrow, I am going to check this. The problem is that the fault is not a fixed one, but goes back and forth: the truck is sometimes fine and other times not.
By the other hand, I was checking the O2SB1S2 and I think is ok, it is giving between 0.425 V and 0.47 V (readings took in two different times), but the readings in the other one, O2SB1S1, are between 0.03 V and 0.125 V (readings took in two different times). I am taking this reading with an scanner Innova 3040.

Okay That is great info. I highly expect the EVAP purge solenoid is failed. This would indicate why it runs better when the fuel level is different.

This sticks at times and will cause all sorts of engine running issues. Basically when it sticks open it floods the engine and it will cause these types of issues.

I attached the process below to replace this. I would also inspect the charcoal canister for raw fuel in it. If you hear fuel in it then I would replace that as well.