Idling too fast

There are no codes, Truck has only been tuned up, plugs and wires.

Engine Performance problem
1999 Ford Ranger 6 cyl Four Wheel Drive Manual

hi.I have a 1999 ford ranger 4.0l ohv with 5 speed manual trans. Sometimes when coming to a stop and pressing the clutch in, the rpm's will hang around 1300-1500 and then slowly drop back down around 800.I have a scan tool and noticed that when I release the throttle no matter what the rpm stays at the tps pid always reads around 18.4%. To me that says the throttle plate is closed and not hanging up. LTFT and STFT read in the correct range(between -10%-+10%)
but the maf when the idle hangs up reads 1.1lb per mile, when it idles normally maf reads.55lb per mile. This is a new maf sensor from napa. Is this a defective new maf sensor or am I barking up the wrong tree. Also I know there is a t.S.B. For this but I cannot find the calibration code in the usual places to see if my vehicle is affected. Thanks.

Yes, tried new one and did the same thing. But if I drive with the iac valve disconnected rpm drops normally.

While I'm driving, every time I take the truck out of gear it revs up to about 3,000 rpm unless I come to a complete stop where it will fall back down to 1000 rpm. I replaced the throttle control sensor on the throttle body. It was driving fine after that but then leaving the truck sitting for a week the problem only came back. Also trying to start is a problem unless your foot is down all the way on the gas pedal.

Thanks I will try that.

No the check engine light has not come on.

My problem turned out to be a leak in the lower gasket under the pental on my 95 4.0 ranger, the dionostic cost me 150.00$ they wanted 500.00 to fix it, I bought the book and fixed it myself for twenty bucks.

Hello, When started engine idles fast then slows down, but it doesn't seem top be enough. Used to get 21 mpg, now get 16mpg.

When the cluth is disengaged and the truck should be decelerating the idle races untill the truck comed to a stop. Happens intermitintly aslo if I punch the gas pedal real quick the idle returns to normal. Have also experienced the idle throttling up by its self.

There is a vacum hose on the valve cover next to the oil fill that runs up to the throttle that was dried and loose. Changed the hose with a new one and 2 hose clamps and the problem stopped.

My ranger was running ok when I took it to a Ford Dealership to replace a leaking valve cover gasket. The throttle body was removed and cleaned also. Now when you accelerate and then decelerate the idle will not come down as it should it may take 10 to15 seconds for it to idle back down. It will do this each time whether it is hot or cold. The IAC valve has been changed twice. What else can it be? Lash Formby