Question about 2000 Ford Ranger SuperCab
Hello... The first thing to determine is whether the high idle is caused by a mechanical issue, such as a faulty idle air control sensor (IAC), or a throttle plate that is not closing, or if the idle speed is actually being commanded high by the computer. One of the easiest ways to do that is to simply unplug the IAC with the truck at idle, and allow the engine to slow to the "minimum air rate" or base idle speed. There is no published spec, but if your minimum idle speed is in the 500-600rpm range in park, thats close enough. There is no normal service adjustments required, but if something is keeping the throttle plate from closing, then you'll have to correct that.
Now...when you unplug the IAC, you will find either a normal minimum idle, or no change at all. If there is no change, and the throttle is not sticking open, suspect air is getting around the throttle plate, which could be a bad IAC, because thats exactly what it does, it allows air to enter the engine around the throttle plate. Normally the computer has complete control of the IAC, but it can fail mechanically, so it must be checked.
The next scenerio would be the idle speed being correct when the IAC is unplugged, and then going back up when it's plugged back in. This would indicate the computer is actually commanding the idle speed high....and this is where the correct scan tool becomes so important, because it allows the techincian to see this information right from the computer. From this info the problem can be determined and repaired.
Good luck..i hope this helps...please take time to rate me a fixya.
Posted on Jul 23, 2009
Low / uneven idle problem can cause by a lot of components.
Dirty air filter
Dirty injectors + o-rings
Vacuum leak at intake manifold and vacuum hose.
Bad Idle Air Control Motor (IAC)
Low compression (170 psi + is OK)
Start cleaning and repair these trouble spots and see is there any improvement.
For more advance DIY'er then you may try this.
Use a can of Berryman carburetor clean to locate the vacuum leak.
SEE SAMPLE PICTURE HERE
This is a 20-30 minutes job.
Vacuum leaks can occur in following locations.
Intake manifold AND/OR vacuum lines.
Intake manifold is not accessible unless the engine head if off.
You can still check the potential leak by spraying some Berryman near the intake manifold.
Listen for rpm increase after you introduce the Berryman (FUEL) at idle.
Do the same starting from the brake booster unit (the round unit) on the drive side fire all.
Carefully listen for increase of RPM right after to spray the Berryman to the potential vacuum spot.
Get a friend to HEAR the ROM increase or monitor for RPM on the tech.
DO NOT AIM the Berryman into any heat source.
PLEASE RATE my answer if it is useful to you.
Posted on Dec 14, 2009
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Posted on Jan 02, 2017
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