Got an issue I need help with, when I come to a stop engine wants to tach high, but when I leave the clutch out and put a load on it I can pull it down to an idle, it does not do this all the time which is why I can't figure it out. I've replaced the iac valve, tps sensor, and timing belt so far. Now lately it seems like when I shift gears the motor will rev up in between gears. It does not have a tach so I can't say where it is at. A ideas what is going on is appreciated

 

After engine is warmed up and idling, unplug the wires from the IAC Valve.
Idle should drop down to 500(barely running) or engine may even stall, either is good, it means no vacuum leaks.
If idle stays high then there is an air leak somewhere.
Start checking hoses while IAC is unplugged.

If idle drops down or engine stalls then the Computer is running the higher RPM, could be a few reasons for that.
But do IAC test first

 

I tried iac test, when I unplugged it it just gave the truck a low idle, nothing rough. When I plugged it back in the rpms picked back up again. I've been reading similar threads, do you think a MAF sensor could be a possiblitly? I'm just surprised I'm not getting any engine codes

 

Then no vacuum leaks.

MAF sensor is unlikely cause, it's function is to report air flow, while this will effect Lean/Rich fuel mix I can't see it effecting RPM directly.
They do need to be cleaned every 5 years or so.

Actual air flow controls engine RPM, with throttle plate closed you can add more fuel but RPMs won't go up, engine just runs richer until it stalls, if you reduce fuel, engine runs Lean and pings but RPMs remain the same.
As more air is let in the engine RPMs go up, which is why vacuum leaks increase RPMs, and it is how the IAC valve works, computer lets in more air to increase RPMs, reduces the air flow to decrease RPMs.

Couple of other things to check.
Do you have Cruise Control?
If so remove that cable from throttle linkage, tape it out of the way.
Drive truck a few days to see if RPMs act normally.
Cruise actuator could be failing and pulling throttle open now and then.

Also with throttle cable linkage exposed, remove throttle cable and operate throttle manually to see if it is sticking, also that it's spring is not broken.
When engine is running the air flow passed the throttle plate will hold the plate open unless spring can pull it closed when you take your foot of the gas pedal.

Also remove the plenum air tube, and feel if the throttle plate is tight to the shaft.

 

No cruise control. What are you calling the plenum air tube? I've never heard of this before

 

From the air cleaner to the intake is a tube for the air.

Plenum has a few definitions, one of them is a chamber filled with air at a different pressure that outside the Plenum

 

Not quite sure of what you may be talking about, I attached a pic of what I think you are talking about, but I don't see what you want me to check

 

It is the tube with the ribs on it.
That should run to the intake manifold, if it is removed you should be able to see the throttle plate inside the intake manifold.

Gasoline engines run on air mostly, the way you increase and reduce the RPMs is by controlling the air flow into the intake/engine.
The throttle plate does that, when closed very little air can be sucked in to the engine, this is what creates the "vacuum" inside the intake, a running engine is HELD at a lower RPM because of this air restriction.

If throttle plate is loose then air can get around it causing RPMs to go up.
If spring holding throttle plate closed is weak vacuum in the intake can pull it open.

"Give it some gas" is a misnomer, "Give it some air" is more accurate when talking about increasing engine RPM.

IAC Valve does that, it is located on an air passage that bypasses the throttle plate, IAC Valve lets more or less air into the intake to control engine RPMs when throttle plate is closed.

 

Spring is good, plate seems to be tight. I just don't know why it feels like I have a loss of power and when I shift it either wants to rev up or sometimes like the rpms drop and when I leave the clutch out it wants to grab weird