I have a 2000 ford ranger 170k miles I keep having a high idle issue I have read the forums on here an I dont think I have the same issue as the rest of the people on here anyways when the engine is warming up it idles down but when it warms up it will idle around 12 to 1500 rpm I have replaced the tps and tried 3 iac valves most of the time when I come to a stop and the idle is height I hold the break an let out on the clutch and itll drop and stay at like 850 to 900 rpm... idk what else to do I dont want to take it to the shop cause I'm sure its something I'm over looking, when I plug my bluetooth in to the obd2 I watch the duties on the injectors they stay between + or - 5 to 7% I dont think I have vac leaks I have checked all of them and found one an fixed it and it ran better but I think it has something to do with my iac wiring harness................any feed back will help thanks.



edit when I had the vac leak the fuel trim was -17 -26
now they are around normal

 

Have you cleaned the throttle butterfly ...

 

Welcome to the forum

After engine is fully warmed up and idling......unplug the IAC Valve's 2 wires
IAC Valve should close and RPMs should drop to 500 or so, engine may even stall, either is good, it means no vacuum leaks

If RPMs do NOT drop then you have a leak

If RPMs DO drop then you will know the Computer(PCM) is causing the high idle, it controls the IAC Valve and monitors RPMs so it is opening IAC Valve to set the higher idle.
Most likely a software glitch or PCM would set a code for RPMs not responding to IAC Valve control
PCM "thinks" all is well with 1,300RPM warm idle, which it shouldn't

Call a Ford Dealer with your VIN number available, give it to them and see if there is a software update for your PCM, most likely there is
Dealers do charge for the time it takes to do the upgrade


Not IAC Valve wiring
IAC Valve gets 12volts with key on, the red wire, other wire runs to the PCM and is the Ground
IAC is a solenoid with a spring to hold it closed, the PCM Pulses the ground wire to pull the valve open against spring pressure.
When you turn on the key the PCM grounds the IAC Valve to open it fully for start up, this is why engine should REV above 1,500 any time you start it
After startup the PCM starts to pulse the ground to close the IAC valve and set RPM level
This method of control is accurate to +/- 3RPM

IAC Valve fully open would be 2,000+ RPMs, so PCM is in control, just doing it wrong

 

RON thanks for your knowledge I will try everything you say... what I have tried so far, I have the OEM an a another brand of iac when the truck is not running with key on I have tried plugging in two different iac and the solenoid does not move at all, for the last month or so I have been driving with the iac unplugged cause it's the only way I can get the 3.0 to run somewhat normal, even sometimes with iac itll still idle high and out of know where drop down to normal idle and sometimes itll drop down right after I come to a stop and sometimes not.......... it does run better with out iac

EDIT- I plugged in the iac and on the warm up start it started at about 2000k dropped to about 15 for about 45 sec then dropped to a good idle... backed out of my spot started to take off and If i touch the gas pedal any little bit itll make the rpm jump back up to 1500 or so and if I stop while it's cold itll come back down it's just when it warms up and itll try holding the idle at 1500 even on my dash but on my bluetooth its actully few 100 rpm off, now when it's hot and idling at 1500 when I unplug the iac it does drop to a 850 to 900 idle havent ever seen it get below like 757rpm..... I'm thinking that because i plugged the iac back in the pcm isnt used to seeing it so it acting a little different then it should trying ro learn things again so I'll drive around with it an see if it relaerns it or not

 

I have not cleaned the butterfly it is a little dirty but I havent touched it is there anything I can do with my bluetooth obd2 reader that can point me to the direction I'll call my local ford dealer an see what they say about updates I'll also plug my iac back in but when I do the idle is so high and I can just watch my fuel gadge dropping lol and sometimes when it teyes to come off high idle the engine shakes a little like of theres alot of fuel or something I watch my stick **** shake then it stops after a min or an runes smoother if I need to I'll make a video on YouTube and show you guys what it's doing
thanks guys

 

Just got off the phone with Henry F him self gave them the vin and they said no active recalls or updates

 

Some one may have messed with your anti-diesel screw
Every one should know that you can't use an "idle screw" with fuel injection, no idler Jets

Which is why ALL fuel injected engines use an "air valve" to control idle, not a Ford thing, all car makers use the same method
Ford calls theirs an IAC(idle air control) valve
On the throttle linkage is what "looks like" an idle screw, it isn't, although it can force idle higher than it should be if incorrectly adjusted, also messes up TPS(throttle position sensor)

Just to take this off the table, you should make sure it is adjusted correctly
Warmed up engine, idling, IAC Valve unplugged
If engine doesn't stall when IAC valve is unplugged then there may be a problem with the anti-diesel screw
Locate screw, turn it counter clock wise 1/2 turn
If idle doesn't change then turn screw back to where it was, you have a vacuum leak
If idle starts to drop then turn it another 1/2 turn, and another 1/2 turn until engine is barely running, 500-600 RPM
Its set

Plug IAC back in and idle should go up to 750-800

IAC valve doesn't need to move much, maybe 1/4"-3/8" movement at most
You can hookup IAC valve to 12v and ground when its off the engine to see its movement, its a solenoid so there is no Polarity, no fixed + and -
As long as one connection is 12v and the other ground, solenoid will move its full range

With key on, engine off, the IAC wires should read 12volts, battery voltage, so 12.3 to 12.8volts, it not then check red wire for 12v using engine as a ground

Have you changed PCV valve recently, PCV system is a controlled vacuum leak so dirty PCV valve can cause higher idles

 

I have had the truck for 3 years now I havent touched the throttle plate screw it used to run fine I had an issue with my battery terminal clamp and it might have rest the computer alot cause it would lose connection do you think that could mess up the pcm? I also got my old iac and plugged it in had a buddy turn the key on and I could feel the iac doing something with it in my hand but it wasnt moving at most it would move like a 1/16 of an inch and that was all took the new one off and did the same exact thing I know for sure when I unplug the iac when its idling high it does drop then I plug it back in and the idle stays down i noticed with ot plugged in it really makes it a chore to drive i hate it, it keeps the idle around 1500 during shifts and it feels like when I let off the gas the truck has no deceleration below 2 grand...I can have it in 4th gear and itll push it about 35 mph and I push the clutch in at it jumps up to 1500

 

Couple of things

First, it is normal for RPMs to "hang" when shifting gears, but with clutch pedal down that should last less than 10seconds and then RPMs should drop to about 1000
Second, RPMs should stay around 1000-1100rpms idle until speedometer is under 5MPH, then idle should drop to 650-750 depending on emission standards in your area
These are emission requirements

No, resetting computer shouldn't hurt it, the chips inside run on 5volts so their power supplies are either on or off, fluctuating 12volt power won't hurt anything physically, the computer system was designed for variable voltage use, all vehicles run with voltages between 12 and 15volts

So you don't think there is a vacuum leak, and you don't think the IAC valve is at fault, and the throttle plate is OK
Then problem is the computer

Software glitch can be because computer is skipping over some code, because it "thinks" it should, computer "thinks" all is well even with the high idle or it would set a code

 

Yeah its really bad when I plugged my old and new iac in and turned the power on it only glitches or pulsed a little bit but really didnt move at all and it stayed shut most of the way.
when I'm driving and get the idle to come down by letting out on the clutch a bit itll idle down and stay there but if I touch the pedal the slightest bit or even if I do it by hand with the throttle blade mechanism itll jump up to 1500 and stay and I tried pushing in on the clutch and held it down but it wouldn't come down unless I unplugged the iac or let out on the clutch.

What is a normal vaccume pressure for the 3.0l vulcan?

And if it is the pcm how do I go about that can they re flash it at a tune shop or something or just find one out of a junked ranger?

 

Vacuum pressure doesn't very by engine, it varies by elevation though

18-21" of vacuum at idle is expected, subtract 1" per 1,000ft above 2,000ft elevation

You can't detect a vacuum leak with a vacuum gauge, lol, I know weird

Test IAC valve with 12volt battery directly, see what its travel is

 

Thanks ron I finally feel like I getting somewhere ima do a few test an I'll let you know what happens I'm gonna attempt a smoke down test then check the iac one more time on a 12v battery and then we will narrow it down some more