Idling too fast

Tiny
BATMAN4U_Y2K
  • MEMBER
  • 1999 FORD RANGER
I have a 1999 ford ranger xlt. 2.5l. 5 speed. With 67000 miles. Im having trouble with it idleing too fast in Neutral at a stop light. The IAC has been replaced and no Vacuum hoses are broken or unattached. Any more suggestions would help alot. My mechanic is stumped because it doesnt do it all the time. It will also idle real fast when I push in the clutch to change gears then drop off after shifting gears.
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Tuesday, July 17th, 2007 AT 5:56 PM

50 Replies

Tiny
JACK42
  • MEMBER
Any codes in the PCM? What work besides the IAC has been done to the truck?

This guide can help us fix it

https://www.2carpros.com/articles/engine-idles-too-high

Please run down this guide and report back.
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Monday, July 23rd, 2007 AT 7:30 AM
Tiny
BATMAN4U_Y2K
  • MEMBER
There are no codes, Truck has only been tuned up, plugs and wires.
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Wednesday, July 25th, 2007 AT 7:20 PM
Tiny
JACK42
  • MEMBER
So it only does it sometimes? What kind (brand) of IAC did your mechanic use?
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Thursday, July 26th, 2007 AT 7:52 AM
Tiny
CANNON302
  • MEMBER
  • 1999 FORD RANGER
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Have you checked the IAC?
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
CANNON302
  • MEMBER
Yes, tried new one and did the same thing. But if I drive with the iac valve disconnected rpm drops normally.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
I would recommend trying a different MAF. You could have gotten a bad one.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
ONEPUNCHMAC
  • MEMBER
  • 1999 FORD RANGER
  • 6 CYL
  • 2WD
  • MANUAL
  • 287,000 MILES
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Has the check engine light come on?
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+1
Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
CANNON302
  • MEMBER
Thanks I will try that.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
ONEPUNCHMAC
  • MEMBER
No the check engine light has not come on.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Let me know if it helps.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
It sounds like a bad throttle position sensor, but I can't be sure without the check engine light. Therefore, start by checking for vacuum leaks.

Let me know what you find.

Joe
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
GET123GOT
  • MEMBER
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
1999FORDRANGER
  • MEMBER
  • 1999 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 89,000 MILES
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
RENAUDTN
  • MEMBER
You could try to clean your IAC valve, it may help with your idle problem and your poor fuel consumption. Also check your IAC motor.
I would also clean the MAF sensor, replace the air filter, inspect/replace the spark plugs and the whole ignition. In a nutshell get a tune-up. It should help with your fuel economy.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
That could be the problem with this one too. Vacuum leaks cause all sorts of problems.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
TOMW99
  • MEMBER
  • 1999 FORD RANGER
  • 4 CYL
  • 2WD
  • MANUAL
  • 101,000 MILES
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
TOMW99
  • MEMBER
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.
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Monday, January 6th, 2020 AT 10:09 AM (Merged)
Tiny
LASHLARUE
  • MEMBER
  • 1999 FORD RANGER
  • 2.5L
  • 4 CYL
  • 2WD
  • MANUAL
  • 172,000 MILES
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
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Monday, January 6th, 2020 AT 10:10 AM (Merged)

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