If the truck is below 1500 RPM, at 1000 RPM for example, and I touch the gas it pulls itself to 1500 RPM, as if the throttle is sticking to 1500 RPM. It is very specifically to 1500 RPM. The TPS is new and I just cleaned the IAC. Even when I had the brand new IAC it still did this. I unplugged the IAC and TPS separately and tested if this “stick” would go away. It did not. I hit every vacuum line with starter fluid, did not find any vacuum leaks. Also checked each line individually. Idle is around 900 RPM and refuses to drop below. If during the “stick” I press the clutch it will act as if I hit the clutch and revved the engine, it will jump up then come back down to idle at 1100 RPM (while rolling). This is a 5 speed manual, 3.0 4x4. 1998.

 

If you have unplugged your IAC while idling with no change in RPM's you have a vacuum leak somewhere. Unplugging the IAC should cause the engine to either stumble or stall out. Also, these Rangers will hold high idle, while moving, until they get below 5 mph. Its an emissions thing. Engines put out less pollutants at higher idle than low idle

 

The RPMs did drop when I unplugged the IAC—and I figure the RPM only drops when under 5 mph, but it stays abnormally high around 1500 and then drops to about 900–1100.