I have a 94 Ranger 4x4 with a 2.3L. when I bought the truck it did not run and the timing belt was broken. Upon further investigation I found a bad head (cracked) and bought a new head and installed it as well as the timing belt, thermostat housing, thermostat. serpentine belt, fuel pump, battery, plugs and wires. I have a issue with the truck wanting to idle at around 1200 RPM however it will fluctuate while in neutral from 1200-1500 RPM. Occasionally it will even go up to 2200 or so RPM. I have read that it could be the TPS, IAC valve, MAF Sensor, and even the PCM. If anyone knows a way I can troubleshoot my problem I would be very grateful. Also just today I ended up with a very loud hissing while driving down the highway at around 70MPH, no loss of power just the noise. Sounds like someone opened a pressure release valve on a air compressor. Noise gets louder upon acceleration.

 

Sounds like you have a broke or cracked vacuum line.

 

How exactly would I go about checking those lines. I have no idea where they are at just an fyi.

 

How do I go about cleaning the IAC?

 

IAC(idle air control) valve, is how the computer sets the idle level on a fuel injected engine.
There are no Jets like a carb had so an idle screw won't work.
Not a Ford thing, all fuel injected engines use an IAC valve, might be a different name but same device.

Computer slides this valve open a bit to let in more air which increases the idle RPM, and closes it a bit to decrease the air and lower the RPMs, pretty simple.

But if you have an air leak(vacuum leak) then even if computer closes the IAC valve all the way it can't lower the idle below a certain RPM because of the air leak.

Simple test is to warm up the engine and let it idle
Find the IAC Valve, it will have 2 wires connected
Unplug those wires, with no power the IAC Valve will close all the way
So idle should drop down to about 500rpms or engine may even stall, either is good it means no vacuum leaks.

If idle stays high the first thing to check is to see if someone has messed with the anti-diesel screw, it is on the throttle cable linkage and "looks like" an idle screw, but it isn't.
Unscrew this screw to see if idle starts to drop, if it does then keep unscrewing until idle is low, 500rpms or just about to stall if you don't have a tach.
If unscrewing doesn't change idle then return screw back to original position.

OK, idle is high and it isn't the anti-diesel screw
There will be several vacuum lines/hoses on the intake manifold
With IAC Valve still unplugged and engine still idling, remove 1 hose at a time and plug port with your finger, if RPMs drop you found the hose with the leak
Start with larger hoses like power brake and PCV hoses

 

Thank you Ron D. I will be performing these tests shortly. I have work till late tonight so I probably won't do anything till Friday with the truck.

 

My problem ended up being a vacume line to my egr. Good luck to all with the same problem.

 

Good work on finding that

Thanks for the fix and the update

 

I narrowed everything down the the EGR, TPS, MAF, TAC sensor. After I narrowed all that down I started testing them one by one. When I got to the EGR I pulled the vacuum line and the whole vacuum like was in my hand so I decided to take a closer look at the line and it was almost severed in 2. Replaced the line and started the truck. Truck now idles at a comfortable 700 rpm. It sounds rough though due to an exhaust leak right after the catalytic converter.