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High idol 4.0


Ohhnulix

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I recently bought a 01 4x4 4.0. The only issue I’ve found is a high idol, about 1800rpm, when I turn the ac off it jumps to about 2000, I would imagine that a vaccum leak would make the hubs not lock and all that seems fine, any ideas? No check engine lights or codes. Only other issue I’ve found is a kinda sticky gas pedal, like it’s hard to move at the top but after it moves it’s fine and free
 


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RonD

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2002 Ranger doesn't have PVH front hubs, just 1998-2000 Rangers did, your front hubs are bolted to the front axles, always locked

Warm up engine
Let it idle
Unplug the 2 wire connector on the IAC Valve
(looks like this, upper front of engine: https://www.ford-trucks.com/forums/attachment.php?attachmentid=594&stc=1&d=1062021739 )

Idle should drop down, engine may even stall, either is good
If it doesn't drop then you have a vacuum leak

OR
From your other comment, "Only other issue I’ve found is a kinda sticky gas pedal..."
You may have a throttle plate issue, its sticking and not closing all the way
I would check this first
Pull off the "air tube" from intake manifold so you can see the throttle plate inside intake
Manually move the throttle linkage to see if its sticking, try to pull it closed more
If TPS(throttle sensor) was ever replace someone may have goofed up and its whats causing the "sticky gas pedal"


Common vacuum leak on the 4.0l SOHC engine is the PCV Hose, at the elbows
Thread here on that issue: https://www.ranger-forums.com/4-0l-ohv-sohc-v6-tech-33/pcv-elbow-fix-very-common-cel-93776/

This is usually associated with Lean Codes, because of the vacuum leak

My bet is on the "sticky gas pedal" causing the high RPMs
 

Madman54

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My credo
Stop skipping steps and get it done right the first time.
I would agree with what RonD said. sticky gas pedal = something holding it in a position that should be holding it. if the throttle plate isnt the issue check the actually cable where it hooks to the Throttle body....
Just recently I went to look at a car for someone, and a piece of the plastic from the engine cover had snapped off and landed in the throttle cable, causing it to stick about mid throttle leaving them with nothing to do except pull over and call someone. look for something on the gas pedal end that might be causing it too.
then theres the possibillity that the actual throttle cable needs to be replaced, but its not likely.
 

DILLARD000

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Ditto above items.
Also check the ThrottleBody minimum set screw on the right end of the ThrottlePlate axis;
previous owner could have messed that up & set it at too high rpms.
Your warmed up idle should be 650~750rpms; cold start idle is controlled by the IACValve.

PS: Your 2001 has a "live" front axle\differential, meaning it's always turning when the front wheels are rolling,
unlike previous versions with the vac controlled hubs.
 

Ohhnulix

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Ditto above items.
Also check the ThrottleBody minimum set screw on the right end of the ThrottlePlate axis;
previous owner could have messed that up & set it at too high rpms.
Your warmed up idle should be 650~750rpms; cold start idle is controlled by the IACValve.

PS: Your 2001 has a "live" front axle\differential, meaning it's always turning when the front wheels are rolling,
unlike previous versions with the vac controlled hubs.
I would agree with what RonD said. sticky gas pedal = something holding it in a position that should be holding it. if the throttle plate isnt the issue check the actually cable where it hooks to the Throttle body....
Just recently I went to look at a car for someone, and a piece of the plastic from the engine cover had snapped off and landed in the throttle cable, causing it to stick about mid throttle leaving them with nothing to do except pull over and call someone. look for something on the gas pedal end that might be causing it too.
then theres the possibillity that the actual throttle cable needs to be replaced, but its not likely.
2002 Ranger doesn't have PVH front hubs, just 1998-2000 Rangers did, your front hubs are bolted to the front axles, always locked

Warm up engine
Let it idle
Unplug the 2 wire connector on the IAC Valve
(looks like this, upper front of engine: https://www.ford-trucks.com/forums/attachment.php?attachmentid=594&stc=1&d=1062021739 )

Idle should drop down, engine may even stall, either is good
If it doesn't drop then you have a vacuum leak

OR
From your other comment, "Only other issue I’ve found is a kinda sticky gas pedal..."
You may have a throttle plate issue, its sticking and not closing all the way
I would check this first
Pull off the "air tube" from intake manifold so you can see the throttle plate inside intake
Manually move the throttle linkage to see if its sticking, try to pull it closed more
If TPS(throttle sensor) was ever replace someone may have goofed up and its whats causing the "sticky gas pedal"


Common vacuum leak on the 4.0l SOHC engine is the PCV Hose, at the elbows
Thread here on that issue: https://www.ranger-forums.com/4-0l-ohv-sohc-v6-tech-33/pcv-elbow-fix-very-common-cel-93776/

This is usually associated with Lean Codes, because of the vacuum leak

My bet is on the "sticky gas pedal" causing the high RPMs
;
I figured out my issue. Previous owner must have left the air cleaner box open or something, a butterfly got sucked into the intake, got sucked into the IAC valve and left it hung open. I cleaned it out and it worked fine. Next time I fired it up the motor hung open again so I just replaced it, now it runs like a champ
 


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