truck idles high the drops down to normal idle
 

I have a 92 ramger, 4.0. I have put a new air intakw, maf senor, tps, iac and fpr. When I start it, the idle goes up to about 4000 then after a minute or so drops down to normal but when I start driving it will go high until I stop. What could be causing this issue? Thank you all

Start engine and then open the hood and see if you can pull throttle closed more, throttle could be sticking open a bit

Engine off open and close throttle manually and let it "snap" closed, the spring on the throttle must be strong to hold it closed with 18 inches of vacuum trying to pull it open

Warm up engine, 5 to 10min drive
Let it idle and unplug the IAC Valve's 2 wire connector, RPMs should drop to 500 or engine may stall, either is GOOD, it means no vacuum leaks
If RPMs do not drop then you have a vacuum leak, and a good size one for over 2,500 RPM
So start pulling hoses off the intake, one at a time, and plug that intake port with your finger, when RPMs drop you found the system with the leak, follow that hose

IAC valve???
 

Sorry for the dumb question but what is an IAC valve, and where is it located? Thanks

The IAC valve is the idle air control and its located on the top of the driver side engine block. Like close to the hood top. Its about 3 inches long, has a plug on the end of it and has two bolts into the engine

Thanks. Always looking to learn about my Ranger. Can't afford the $90/hr. shop charge!

You said you put in a new IAC Valve?????
Its important to be clear when diagnosing a problem over the internet, you are there, "we" are not
Did YOU put in a new IAC Valve, or do you "think" someone else did?