99 ranger

[Daniel warders]

My 99 ranger with 4.0 liter idles fine in park or neutral but put it in gear and under a load it barley will go and acts like it is going to die. If given enough time and space to ger up to speed slowly it will start to seem to run fine till i have to slow down again and it then does the same. Barley runs ..have changed the fuel filter. New fuel pump. Not sure what to check next

 

[RonD]

Welcome to TRS

Fuel injected engines use an air valve to set idle, on Fords its call the IAC(idle air control) Valve

Its a 2 wire solenoid that looks like a can laying on its side, its near the throttle plate on upper intake, find it
Pictures of one here: https://www.explorerforum.com/forums/threads/iac-valve-cleaning-thread-w-pics.84220/

After engine is warmed up and idling in Park/Neutral
Unplug the IAC Valve's 2 wire connector, valve should close and RPMs should drop to 500 or engine may even stall, either is good it means IAC Valve is working
If Idle doesn't change it means its not working, its stuck at one place
When you shift into gear the computer should bump up the idle, open IAC valve more

Also IAC Valve is used on Cold starts, idle should be 1,100rpms on cold start and then drop down to 750 after 5 minutes of warm up, in gear it should be 825-850
Does engine do that?

There is a screw on the throttle linkage that "looks like" an idle screw, but every one knows fuel injection can't use an idle screw because there are no Jets, right, lol, its an "anti-diesel" screw and should not be adjusted unless there is an issue with throttle sensor


There is also an ECT(engine coolant temp) sensor, its a 5volt sensor only used by the computer to set CHOKE MODE when engine is started cold
ECT sensor is how computer knows what idle RPM to set with IAC Valve
ETC sensor is just above thermostat housing on a 4.0l OHV
But next to it is the 12volt SENDER for the dash temp gauge, and they look similar, sender will have a red/white stripe wire
ECT sensor will have a grey/red stripe wire

 

[Daniel warders]

Thanks RonD. Goong out to try that now. Ill let u know

 

[Daniel warders]

Well I unplugged the iac. Idle dropped as u described so its working. Dont think that is the problem