Your Ford F150’s engine can be adjusted if it sounds off or the RPMs are up and down when idling. With a flathead screwdriver and a warm engine, it’s possible to manually adjust the idle on a Ford F150 in 5 to 10 minutes. In simple terms, this is how you do it, followed by more detailed step by step instructions.
How do you adjust the idle on a Ford F150? The F150’s idling screw must be quartered. Turning the screws to the right increases the idle speed. If too fast, move it to the left. An engine fault can’t be fixed by this procedure, but it can protect your car from falling or running too hot, which can damage the engine.
How do adjust idle on a Ford F150
On the driver’s side of the carburetor, the main throttle linkage has an idle speed adjustment screw that controls the curb idle. Begin by adjusting (clockwise) the idle mixture screw on the driver’s side by about 1/8th of a turn while keeping your vacuum meter handy.
Step 1: Get ready to fine-tune your idle.
After your Ford F150’s engine has been running for a few minutes, shut it off. Turn the ignition key to the “off” position. Do not remove the key from the ignition switch.
Step 2: Determine the location of the idle adjustment screws
With a wrench, disconnect your vehicle’s negative battery cable. Use gloves, as touching both poles of the battery can result in serious injury or electrocution. The screws are on the top of your engine, near where your throttle control cable meets the throttle plate. You can open your hood and look for one of the screws.
These screws are small and may look like they are part of another component on your F150. The screw closest to where you inserted your negative battery cable is for idling speed adjustment; this is called a “fast idle screw,” and it adjusts idle speed very quickly without having to turn an adjustment screw first.
The other is an adjustment screw that must be turned first to reach the fast idle screw.
Step 3: Tighten your screws
Turn your fast idle screw counter clockwise to lower your F150’s idle speed. You mustn’t turn it too far, as this will cause your engine to stall and may damage your motor. Do not leave the adjustment screw loose, as it can fall out and cause damage.
The fast idle adjustment screw should only be turned a small amount; less than a quarter-turn is usually sufficient.
If you cannot turn the fast idle adjustment screw any farther without loosening it or taking it out of its hole entirely, you have reached the correct setting for idling speed.
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Step 4: Reset the oil light on your engine
If you have lowered and adjusted your F150’s idle speed, the oil light on your instrument panel will be illuminated. This indicates that your engine is not receiving sufficient lubrication.
To reset it, simply turn the adjustment screw clockwise until it stops, then back it off a quarter-turn. The oil light should go out immediately.
Step 5: Use the fast idle adjustment screw for a quick check of the idle speed
If you need to check your F150’s idle speed quickly, hold the fast idle adjustment screw with your fingers and turn it clockwise until it stops. This will raise your truck’s idle speed until it reaches the fast idle adjustment screw setting.
Now release the screw and turn it counter clockwise until it stops. This will lower the idle speed to its normal setting. If your Ford truck’s idle speed is not where you want it, repeat Steps 1 through 4.
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Required RPM for Ford F150
If your truck has a 5.0L Triton V8 engine, you need to set the idle speed to a minimum of 700 RPMs. If you have a 4.6L engine, set it at 800 RPMs. If you have a 4.2L or 5.4L engine, set it at 900 RPMs.
For more detail, see this guide that explains the normal idle RPM for F150s in different years and models.
Why your Ford F150 idles up and down
If your Ford F159 is idling too high or too low, one of the following may be causing this problem:
- The throttle body may be dirty and not close completely. This is likely to cause the idle to fluctuate rapidly between very high and very low. It will also cause a rough idle and stalling. If this is the case, you should clean or replace your throttle body.
- If you have an automatic transmission, the shift solenoid may be sticking open or closed. This will cause a rough idle and stalling when you are stopped at a light or in traffic. You should have your transmission serviced if this is the case.
If it’s wilding going up and down, check for these alternative problems.
As you can see, it is possible to manually adjust idle in a Ford F150, providing you know what you’re doing. Make sure you get it set to the right idle RPM for your year and model.