To begin, i have read every single high idle thread on this, and many other forums. there are numerous people that have had this problem but i have yet to find a thread that has a solution, its just the same 5 maintanance procedures people say to do. My particular situation went like this.

My truck has never had any idle issues before this week. I have a thermostat housing leak and when i took the intake system apart to look at the housing more closely, i found that my throttle body was quite dirty. i cleaned it with a lint free towel and throttle and intake cleaner. Apparently there is some special coating or whatever on the butterfly valve cause when i initially sprayed the cleaner on the closed valve, it collected at the bottom of the throttle and sat there, not going through the other side. after i cleaned it completely off(not using my fingers to open the valve) the cleaner would no longer pool on the bottom, it would sit there for a second and seep through the valve and the surrounding throttle body. after everything was put back together, i started having a high idle/ hesitant return to idle. i would imagine that the lack of the coating(which was helping to completely seal the area around the valve) is cause excess air to leak in.

Now, after cleaning every possible item and doing every tiny minute thing to overcome this, i have no choice but to say that the cleaning of the throttle plate and removing all the teflon coating was the problem. I do not see any way that it could not be. i have even gotten a brand new IACV and the problem is the same.

Further evidence....

According to my ultraguage, before i started having any problems, my truck was solidly idling at 750 rpm at 35-42% engine load. after all the cleaning and the new parts and whatever, my ultra still reads 22% engine load always while idling, and the rpms will shift from 800-1100 depending on if i rev the engine at stop, or am cruising or whatever.
When i remove the IACV plug, the car idles smoother, at 750 rpm, but still at 22% engine load and it is much faster to come down to idle speed during a shift, whereas with it plugged in and i go to shift gears, it revs down much slower and sometimes holds rpm. i have no vacuum leaks to speak of either.

i guess my question is, should i get a new factory throttle body and call it a day? or is there some kind of lube or coating i can respray on my valve to make it more airtight? i would really love to dicuss any possible solutions as this issue is exceptionally irritating for me.

 

I have this same problem. It seems to be worse when the a/c is on. Mine didn't start until I disconnected the battery cable.

 

Did u check the tps sensor?

 

Some people argue that the coating is not important but Ford shop manuals warn us not to remove it. Your experience with the idle speed is the reason why.

It might be possible to reduce the idle speed by using the stop screw to close the throttle plate down closer to the bore although this is also not recommended. After readjusting the screw, there could be issues with the plate sticking in the bore when the TB is cold. In certain cases, there might also be a trouble code for the TPS voltage being out of range on the low side.

 

The coating is to protect the throttle body from contaminates sticking too it from the Pcv valve. The coating is too thin to cause an issue unless the tb is caked up and stuck. It could also be the pcv is clogged. I am experienceing the same problem with my truck but I have yet to look into it. If I get a chance today I'm going hook up my scan tool and see what I can find.

 

22% load seems alright for idle in that motor. Set the idle to 500-550 with the IAC unplugged and try that. If the throttle pedal sticks, then it will have to be opened more. What is the IAC duty cycle when it happens? does the scan gauge read that?

 

22% just seems weird to me since i had the truck for a year or so with the ultraguage and it would always sit at about 37% load. Although now that i think about it, since i cleaned the throttle plate, maybe that returned the load to what it was supposed to be at all the time, but why then would the idle speed have changed? i did not mess with the idle screw at all, it still has the factory yellow paint on it signifying the correct location.

i am not entirely sure about the iac cycle, what type of info would that be?

With regards to the TPS, i cleaned the sensor connector but i did not mess with the TPS itself. it was screwed in prettyhard and i didnt not imagine it to have moved when i was cleaning the throttle body. i guess its the only thing to try.....

what makes things more odd is the fact that it seems to idle better(correct 750rpm idle) when the air conditioner is on. although its weird that the engine remains at 22% load with or without the ac on, which when my truck was idleing ok, was not the issue, it would always jump maybe 5% when the ac was on......im flipping pissed about this tiny issue

 

my pcv is brand new, less than 10k miles on it. i change it religiously cause its so cheap and easy to do

 

This is a wild guess but any one think about the evap purge solenoid. I don't think It would cause a problem like this but I've seen weirder stuff happen.

 

strange, how does one go about doing that?

 

The coating is applied to the plate and bore and allowed to dry. After drying, the seal is broken to allow plate movement but it still seals the throttle plate to the bore when the throttle arm is closed to the stop screw. A hole or two of the correct diameter are punched in the throttle plate to allow enough air bleed to maintain a minimum idle speed, typically something like 350~500 RPM with the IAC disabled. The PCM controlled IAC then bypasses airflow around the plate to bring the idle speed up to the commanded RPM. By doing it this way, the base idle airflow and IAC duty cycle remain fairly consistent over the life of the vehicle.

The alternative is to omit the holes in the plate and allow airflow around the perimeter of the butterfly instead. This is fine when the throttle body is new but the gap can fill with contamination over time and change the closed throttle airflow. This contamination comes primarily from reverse PCV flow at or near WOT. Changing the minimum airflow around the plate changes the IAC duty cycle and will also cause more frequent stalling if the IAC fails. Not good.

Consistency is why Ford and many other manufactures use the coating.

If the factory coating is removed, the base airflow is the sum of the flow through the throttle plate hole(s) PLUS the flow through the gap around the perimeter of the plate. The added airflow can push the curb idle speed above the RPM commanded by the PCM. When that happens, the system is out of control.

 

i had ford run a diagnostic, and i was looking at the data with the tech, the truck is running exceptional in every way except the duty cycle for the IAC was at 24% and the tech said it should be at about 35%. this is also a brand new iac. t he said this is usually caused by a vacuum leak but i didnt have one in my case. fuel correction was all less than 5% which is exceptional.

what do you guys think? they didnt charge for my diagnostic cause they could not determine the prob.

also, the tech said he reflashed the PCM so that rules that out.

 

Was that short term or long term furl correction

 

Both short and long were about 5%. Tech said it doesn't get better than that. May have to try a new throttle body soon.

Side note. What do most 4.0s run at temperature wise? The guy said my avg. Of 176-183 is a bit too low but he said every cars different....

 

A small update:

I have driven the truck for about 50 miles, and it seems that the high idle problem has improved some. it still holds idle at 1000 rpm in neutral with the car moving more than half the time, but it seems to return to normal idle faster, rather than not at all beforehand. I think it may just take a while for the computer to relearn everything since the tech did a reflash and cleared the memory on the ecu. i figure after this tank of gas ill run it for codes and see whats up.

 

4.0L M/T - HIGH IDLE BETWEEN SHIFTS OR IN NEUTRAL
TECHNICAL SERVICE BULLETIN
Reference Number(s): 05-5-10, Date of Issue: March 21, 2005
FORD:2004-2005 Ranger

Related Ref Number(s): 05-5-10
ARTICLE BEGINNING
DESCRIPTION
HIGH IDLE BETWEEN SHIFTS OR IN NEUTRAL - 4.0L ENGINE WITH MANUAL TRANSMISSION
ISSUE
Some 2004-2005 Rangers equipped with a 4.0L engine and manual transmission, may exhibit a higher than expected idle between shifts, during a coast down with the clutch depressed, or with the transmission in neutral.
ACTION
Reprogram the powertrain control module (PCM) to the latest calibration level using WDS release B35.9 and higher, or B36.2 and higher. Calibration files may also be obtained at www.motorcraft.com.
NOTE:THIS NEW CALIBRATION IS NOT INCLUDED IN THE B36.0 CD.

WARRANTY INFORMATION
WARRANTY STATUS: Eligible Under Provisions Of New Vehicle Limited Warranty Coverage.

 

You said you had a thermostat housing leak. Perhaps the engine coolant sensor, which is in the housing, was disconnected or is bad. I had a similar high idle problem, but at 1500 rpm, and replacing the sensor solved the problem. An ohm meter can be used to determine if the sensor is bad.

 

About a month ago i replaced the thermostat, thermo housing, and all the sensors. The problem remains. I am convinced it was the throttle body. when i get some extra cash ill get a new one, the problem is not as bad but im sure its not helping my gas mileage havuing the idle a bit off. ill post after i get it changed out and see if it helps at all.....

 

Hmmmm. Im driving a 2000 ranger 2.5l manual w 135000 on it. would some of these solutions apply to me?

 

2005 Ranger 2.3 L ~ 110,000 miles. 5-speed manual

Without any warning my truck jumped up to around 3,500 RPM one day on ignition. And stayed there. Not much wavering, just revving way too high for idle. When in gear and accelerating, it would come down close to normal, but as soon as I put in the clutch or dropped to neutral it would rev high again. Was able to drive most of the way home without shifting higher than third.

Reading this and other forums I figured it was most likely a vacuum leak, throttle issue or problem with the idle air control valve. Listened around for leaks but couldn't hear any. Living in an apt and having to do repairs on the side of the street, I avoided messing with the throttle until a last resort and decided to pull off the IAC valve (a three-minute job) to see if it was obviously dirty or broken.

Turned out there was a small seed stuck in the valve, keeping it from closing and allowing in more air than normal at idle. Pulled the seed out, put the valve back in place and the truck ran like a dream.

Probably not a fix for everyone's problem, but figured I'd mention it since it would have taken me a while to check the IAC if not for it being mentioned in this forum.

 

Too high idle while moving and normal if stop ?
It's traditional and simple problem in many models of car.
TPS, Throttle Position Sensor gives signal to ECU, slightly smaller than necessary.
Attention ! Not only in idle point, but in the middle of working range too.
If this signal is 0,2-0,3V smaller than needed, you have too high RPM if moving and neutral is switched.
What to do ?
The first, most simple: Throttle position sensor can to be installed on throttle axis with little left-right return, few degrees, Make the signal from TPS little enlarge.
Theory of this problem and methods to solve is described here:
??????? ???????? ??? ? ???????????? ???????: ???????? ? ????????? - ?????????? - ??????? ?????? (???????? ???.) - TV-REMONT.INFO
(article is in Ukrainian language, use translator).

 

Did you ever find a solution to your high idol issue. My 98 ranger was doing the same. Stick on high idol when driving. Sitting still in neutral was fine. I found the intake air temp sensor was dirty. Took it out, cleaned it, problem went away. Not the first time I had this happen. My89 bronco II had the same thing happen. This sensor measures the intake air temp and density and relays it to the ecu which uses the info to adjust the fuel mixture. Malfunction can make it run rich or high idol. Good luck.

 

Very interesting. I think I can trace my high idle to about the time the starter was going out. I checked the battery cables and took both off for cleaning. That is when my high idle started. I have since replaced the starter a week ago because it finally gave up the ghost and would not turn over.
I am still looking for possible causes for the high idle out of nowhere

 

high idle ,,,about 3000 at idle
changed idle valve and throttle sensor, checked for stuck throttle cable, nothing has improved it
2002 4.0 where else can I look?

 

Hey just my 0.02:

My idle used to be ~750, then a couple weeks ago it decided to move up to 1500 and the CE light came on with a code for high idle. My MPG's took a drop of 4mpg. So I read this stuff, cleaned out my AIC valve and now it's sitting pretty where it used to around 750 rpm. CE light's off too. Thanks!


I also checked the gas pedal cable for catches. It's a little slack but in good condition, is that a problem? I also checked for vacuum leaks with a propane torch/hose, didn't notice anything out of sorts.

Oh it's a 2001 2.5L ranger