and gain access to Reviews and Discussion of the 2016 and 2017 Ford Explorer Tech Tips, How to Articles, Off-Road Modifications and Events, Street Truck Mods and Events, and much more! Since 1996 our community has covered every aspect of the Ford Explorer, Ford Ranger and all vehicles based on this platform.

Register Today It's free! This box will disappear once registered!

Idle adjustment procedure

Discussion in 'Under the Hood' started by 2000StreetRod, December 10, 2009.

  • Searches ExplorerForum.com
    1. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      There are several threads on the forum describing the idle adjustment process and the following one is very helpful: Idle Air Control Adjustment

      There is also the Ford suggested method that is detailed on the LaSota Racing website. Common Idle Issues/Fixes

      Below are the stock idle speeds (RPM) for my 2000 SOHC V6 with strategy CDE4.

      Idle speed in Neutral (Park) = 656
      Idle speed adder with A/C on in Neutral = 0
      Idle speed in Drive = 624
      Idle speed adder with A/C on in Drive = 0
      MPH for idle control = 0 to 2

      Idle speed adder for ECT
      ECT +RPM
      254 . 544
      230 . 544
      220 . 120
      206 .... 0
      142 .... 0
      100 . 248
      <100 248

      Idle speed adder for IAT
      IAT +RPM
      254 .. 48
      200 .. 48
      190 .... 0
      44 ...... 0
      34 .... 32
      0 .... 232
      <0 .. 232

      The IAC valve is an electro-mechanical device that is prone to degradation and failure with age. Performing the procedure described below will allow the engine to continue to idle at a reduced engine speed when the IAC valve is no longer functioning correctly. I suggest that you perform the TPS Test Procedure before performing the procedure below.

      Your engine should be in reasonably good tune with no vacuum leaks or other problems that would prevent a steady idle.

      It is always a good idea to insure the throttle plate does not stick open or closed.

      There is no hexagon or slot on the end of the screw that contacts a stop on the throttle body when the throttle plate is closed. Turning the screw opens or closes the throttle plate slightly and acts as a mechanical idle adjustment. The red arrow in the photo below identifies the idle adjustment screw.
      IDLESTOP.JPG
      Thread lock is applied to the screw to prevent movement due to vibration. I decided to replace the screw with a socket (Allen) head cap screw M5-.80 x 20 that I purchased from Lowe's. I lubricated the original screw with WD-40 and proceeded to remove the screw by grasping one end with ViseGrips and rotating the screw. This was a very tedious and time consuming process because the very restricted work space limited each turn to about 30 degrees. When the task was finally completed I installed the replacement cap screw using an Allen wrench. I applied WD-40 to the new cap screw instead of thread lock because it was a tight fit and I did not want it to break!

      The vehicle tachometer is not very accurate so I used my X3 Power Flash in the monitor mode to read rpm, desired_idle_rpm, and coolant_temp (engine coolant temperature). I observed that as the coolant_temp increased the desired_idle_rpm decreased gradually to 736 rpm and rpm decreased to 750 rpm with the transmission in Park and the air conditioner compressor not engaged. I experimented with the idle adjustment and the IAC valve connector and learned that the IAC valve controlled idle speed was approximately 200 rpm greater than the idle speed with the IAC valve electrical connector disconnected. I also noticed that actual rpm was approximately 20 rpm greater than desired_idle_rpm. I believe that Ford suggests for a stock engine to adjust the idle speed to 500 rpm with the IAC valve disconnected. Many engine performance modifications detract from a low speed smooth idle. In my case, 550 rpm was much smoother than 500 rpm and resulted in a 750 rpm IAC valve controlled idle. I do not recommend an IAC valve controlled idle speed greater than 850 rpm for vehicles with an automatic transmission. More than that will increase brake wear and transmission fluid temperature and decrease fuel economy. When I selected Drive from Park, the desired_idle_rpm slowly decreased from 736 rpm to 688 rpm. When I switched on the air conditioner the desired_idle_rpm increased.

      My revised version of the Ford procedure is as follows:

      1) If you have a stock tune use the information above to determine the PCM desired idle speed. If you have a custom tune get the information from your tuner. If you have a custom tune and don't know the value you can read the parameter with a scanner or data logger. This will be your target idle rpm. You do not want the throttle stop adjustment to conflict with the PCM controlled IAC valve.

      2) Start the engine and wait for the engine coolant temperature to reach normal operating temperature as indicated on the instrument panel or by OBD monitor. This will take several minutes or longer if a cold start.

      3) Disconnect the IAC valve electrical connector. If the engine stops, turn the throttle-stop screw in one full turn, reconnect the IAC valve electrical connector and restart the engine.

      4) Repeat step 3 above until the engine continues to run when the IAC valve electrical connector is disconnected.

      5) Turn the throttle stop screw to adjust the idle speed to the target rpm minus 200 rpm.

      6) Reconnect the IAC valve electrical connector. The engine speed will briefly flare and then settle. Compare the idle rpm to the target rpm. If satisfactory proceed to step 7. Otherwise, disconnect the IAC valve electrical connector, adjust screw accordingly, then reconnect connector and recompare.

      7) Turn the ignition Off.

      8) Disconnect the negative terminal of the battery cable from the battery. Turn the headlight switch On for 3 minutes then Off and reconnect the battery. This clears stored idle settings and fuel trims.

      9) Start the engine and observe the idle speed in Park and in Drive. If satisfactory be comfortable knowing that in the future should the IAC valve fail, the engine will continue to idle but at a lower rpm. If unsatisfactory, disconnect the IAC valve electrical connector, adjust the throttle stop screw as desired and return to step 6.

      Notes:

      The PCM determines when the engine is at idle by measuring the TPS value when the ignition is switched on and storing it in non-volatile memory. The PCM assumes that the accelerator will not be depressed when switching on the ignition. The PCM periodically checks for a lower TPS value and if one is observed stores that as an updated idle value.

      When vehicle speed exceeds 2 MPH (stock tune) and throttle plate is closed PCM will be in dashpot mode instead of idle speed control.

      If the brake pedal position switch (BPPS) is not functional the PCM will not unlock the torque converter when the vehicle is stopped and the engine will likely stall.
       
      Last edited: March 25, 2015
    2. Support EF


      Join the Elite Explorers for $20 a year

      Explorer Forum has probably saved you that much already, and will continue to save you money as you learn how to diagnose and fix problems yourself, and learn which modifications work without having to experiment on your own. Elite Explorer members see practically no ads, add your own profile photo, upload photo attachments directly to your posts and Media Gallery, create more private Conversations, and more. Join Today. Your support is greatly appreciated.



      to hide adverts.
    3. explorerguy89

      explorerguy89 Active Member

      Joined:
      November 12, 2009
      Messages:
      977
      Likes Received:
      0
      Trophy Points:
      16
      City, State:
      Marlton, NJ
      Year and Model:
      1999 xls and 2000 xlt
      nice guide =] very helpful
       
    4. Nataliator

      Nataliator New Member

      Joined:
      February 8, 2010
      Messages:
      12
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Philly, PA
      Year and Model:
      '97 Sport
      Did this, worked like a charm, thanks alot!
       
    5. dragon6970

      dragon6970 New Member

      Joined:
      November 18, 2010
      Messages:
      1
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      sanfrancisco
      Year and Model:
      1986 eddie bower
      hey can some one help me i have 1986 bronco 11 when i step on the gas my rpms go away then come back any tips
       
    6. silv86

      silv86 New Member

      Joined:
      December 10, 2011
      Messages:
      12
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Pittsburg, KS
      Year and Model:
      01 Mountaineer 5.0 AWD
      I have a 01 mounty 5.0 that when the IAC valve is unplugged does nothing. Any suggestions? I am experiencing the high idle problems...
       
    7. barbaroja

      barbaroja Member

      Joined:
      August 26, 2011
      Messages:
      51
      Likes Received:
      0
      Trophy Points:
      0
      Year and Model:
      1998 Ford Explorer Sport
      I thought the IAC was supposed to be fully closed when coolant temp reached operating temperature.
      If you suspect of a bad IAC, I would phisycally remove the valve and close the holes to avoid the vacumm leak. Then adjust the screw till it runs stable 700RPMs.

      Am I wrong in the IAC operation issue? If the rpms rise as the IAC is connected, that would mean the IAC is not fully closed when in operating temp.

      Pleas someone give light. Thanks.
       
    8. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      commanded idle speed

      I'm not sure about this but I think the PCM reads the idle speed as reported by the crankshaft position sensor and compares that to a desired idle speed table indexed by engine temperature, inlet air temperature, transmission engaged or not and A/C compressor on or off. It then adjusts the commanded idle speed up or down to achieve the desired speed. If the IAC valve was fully closed then the PCM would not be able to lower the engine speed as needed. However, it probably approaches being closed on a very hot day with the engine hot, the transmission in Neutral/Park, and the A/C compressor off.
       
    9. barbaroja

      barbaroja Member

      Joined:
      August 26, 2011
      Messages:
      51
      Likes Received:
      0
      Trophy Points:
      0
      Year and Model:
      1998 Ford Explorer Sport
      Ok that makes sense. Upon further research, the recommended 500 rpm with the iac disconnected makes sense. Those 200 rpms are whats left for the PCM to control it. Yesterday I checked my IAC. I am almost sure its bad. However I thought it was a stepper motor, and the steppers I know have 2the coils; this IAC in my 98 sport has only two connectors. I measured it under operation and got qwvokts when I first turned the car switch on. So I am gessing a regular solenoid there.
       
    10. Bookie

      Bookie New Member

      Joined:
      December 24, 2011
      Messages:
      1
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Magee, Ms.
      Year and Model:
      2005 Ford Explorer RSC
      Hello not sure if this is the correct place to post but in need of some serious help. I have been reading for days on here. I have an 05 explorer xlt 4.0l sohc. I was driving it and it started acting like it was getting no gas. All the way to floor would only go about 5 MPH. Codes where 2104 and 2112. Changes Tps. Changed. Plugs and wires. Idle is best ever till you touch. Gas or it sits running for a minute. Now there are 8 codes. P0122, p0223, p2100, p2104,, p2110,, p2111,, p2195. Any help would be such a blessing. Do not have money to take back to Ford again. Sorry if some of the text is crazy trying to post with phone. Thanks in advance and all have a blessed day. Love this site.
       
    11. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      throttle actuator control

      P0122 Ford TP Sensor Circuit Low Input
      P2100 Ford Throttle Actuator Control Motor Circuit/Open
      P2104 Ford Throttle Actuator Control System - Forced Idle
      P2110 Ford Throttle Actuator Control Motor Processor
      P2111 Ford Throttle Actuator Control System - Stuck Open
      P2112 Ford Throttle Actuator Control System - Stuck Closed
      P2195 Ford Lack of HO2S-11 Switching, Sensor Indicates Lean

      I'm not familiar with the 3rd generation but I think it uses electronic throttle control. From the codes you probably have a problem with the wiring to the actuator motor or the motor itself.
       
    12. Flash

      Flash Well-Known Member

      Joined:
      July 5, 2004
      Messages:
      1,801
      Likes Received:
      2
      Trophy Points:
      48
      City, State:
      Brisbane Australia
      Year and Model:
      1997 Limited
      Are you still looking for answer to this problem?

      It could be an air leak in a vacuum hose somewhere causing a lean condition when you apply the throttle or it could be too much base timing causing a huge misfire.
      The 2nd problem often doesn't cause a backfire but the power will come back with a rush.
       
    13. Timmcnamee

      Timmcnamee New Member

      Joined:
      June 2, 2013
      Messages:
      9
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      St. Charles,MO
      Year and Model:
      1999 explorer
      Great write-up. Will this procedure make permanent adjustments to the idle? I got my idle just right using the adjustment screw and then shut it off, turned it back on and it just dropped to the low idle again....
       
    14. TestPoint

      TestPoint Active Member

      Joined:
      August 21, 2009
      Messages:
      395
      Likes Received:
      1
      Trophy Points:
      18
      City, State:
      Ellijay
      Year and Model:
      '00 5.0 in an '82 Volvo
      '00 302 Explorer 4R70W in an old Volvo. Engine/trans only have abour 11k miles so while old they are not worn out. The only thing that has needed replacing after its 12 year nap in storage has been the injectors. After that everything has run great.

      My idle is too high in drive stopped to the point of vibrating. Disconnecting the IAC drops the rpm's about 200 to about 650 - 700 on the tach. Idles perfectly at that. My OBD II reader displays 816 rpm's with or without the IAC so that is an entirely different issue. I have another one and will check with that shortly.

      Took the IAC off and cleaned with brake cleaner but it wasn't dirty. No obvious air leaks, no lean codes, LTFT 0.00% with new O2 sensors and about a hundred miles since reset. STFT bouncing around +9% at idle which would seem reasonable.

      Is software idle adjustment the next thing?
       
      Last edited: March 12, 2014
    15. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      commanded idle speed?

      My X3 had a default program loaded in it for some type of Ford (I can't remember which one). One of the monitor parameters was commanded idle speed and another was engine speed. You may want to see what's being commanded. As I recall there are different idle speeds for Park/Neutral, other transmission selections, and A/C compressor on/off. The PCM computes a delta between commanded and actual and then factors the delta into the new commanded. It saves the delta in keep alive memory. Since your idle speed drops when you disconnect the IAC valve connector I assume that the engine is being commanded to the higher speed. If the PCM is reading the correct engine speed then your only option is a software modification of the commanded values.
       
    16. TestPoint

      TestPoint Active Member

      Joined:
      August 21, 2009
      Messages:
      395
      Likes Received:
      1
      Trophy Points:
      18
      City, State:
      Ellijay
      Year and Model:
      '00 5.0 in an '82 Volvo
      Since you mention A/C I am trying to stretch my little brain around the fact that the PCM is not going to know the status of the A/C as it will be controlled by the 32 year old Volvo controls. The PCM will know rpm, calculate engine load and transmission status and set the IAC accordingly. I think I would make the assumption that those inputs would cause the PCM to attempt to maintain its commanded rpm level without A/C input.

      I am going to visit James in Hueytown shortly to address several issues and we will add idle rpm to the list.
       
    17. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      HVAC function selector switch

      The PCM monitors the status of the A/C clutch cycling pressure switch which is in series with the A/C pressure cutoff switch. If the pressure is less than 260 psi the cutoff switch is closed enabling a path to ground. The A/C clutch cycling pressure switch is closed when the pressure is greater than 43.5 psi and open when the pressure is less than 24.5 psi. The PCM reads the switch to adjust the transmission EPC pressure. The PCM also reads via Pin 41 the HVAC function selector switch. If battery voltage is present the PCM assumes the selector is in the MAX A/C, NORM A/C, DEFROST, or DEF/FLR position and activates the A/C compressor via the A/C relay except during WOT. If pin 41 is floating then the A/C compressor is not engaged. What do you have connected to pin 41?
       
    18. TestPoint

      TestPoint Active Member

      Joined:
      August 21, 2009
      Messages:
      395
      Likes Received:
      1
      Trophy Points:
      18
      City, State:
      Ellijay
      Year and Model:
      '00 5.0 in an '82 Volvo
      Nothing.

      The Volvo system manages the compressor based on a temp sensitive contact closure located in the evaporator enclosure. I spliced the Volvo system into the the Ford compressor connector just like the the original operation. Saw no reason to involve the PCM.

      Great info that can be applied to other cars.
       
    19. albeegood

      albeegood New Member

      Joined:
      August 27, 2014
      Messages:
      11
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      New Jersey
      Year and Model:
      98 Explorer Sport 4.0
      im gonna try it now ill lat yall know what happens in a few. thx for this info
       
    20. Ck111484

      Ck111484 New Member

      Joined:
      March 15, 2015
      Messages:
      31
      Likes Received:
      0
      Trophy Points:
      0
      Year and Model:
      2002 Explorer
      So does my 2002 Explorer V6 SOHC have an IAC, or no?
       
    21. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      IAC valve if no electronic throttle control

      I think there is an IAC valve on all models that have a throttle cable instead of electronic throttle control that was implemented in 2004.
       
    22. Ck111484

      Ck111484 New Member

      Joined:
      March 15, 2015
      Messages:
      31
      Likes Received:
      0
      Trophy Points:
      0
      Year and Model:
      2002 Explorer
      Hmm, okay, thanks.
      I cleaned something that looks very similar to all the pictures of IAC's that I've seen and in pretty much the same location, but someone told me that if you have a 6-pin MAF (which I do), then you have an integrated IAC and there's nothing to clean.
       
    23. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      Integrated IAT not IAC

      A 6 pin MAF sensor connector means an integrated intake air temperature (IAT) sensor not an integrated idle air control (IAC) valve.
       
    24. field

      field Member

      Joined:
      November 22, 2011
      Messages:
      62
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      California
      Year and Model:
      99 SOHC 2WD EXPLORER
      I got a DTC about my TPS after replacing the thermostat housing. Putting in a new TPS didn't help.

      This guy -

      www.youtube.com/watch?v=FJobCD6y8fk

      shows that the problem is seldom the sensor.
      He is correct in my case. I got this same DTC before and after installing a new sensor. It is:

      P0122 Throttle/Pedal PositionSensor/Switch "A" Circuit Low

      He describes how the MAF, MAP and TPS need to agree in orded to have no DTCs.

      Anyhow, now I always have a roughly running engine unless I hold the pedal down to keep it above above 1100rpm.

      Turning the sensor through it's range while it is out of the intake tube causes some change in the rpm. i.e. I have 5volts to ground where it should be, and a change in rpm while turning the sensor and am mystified why operation isn't normal.

      Any further ideas?
       
    25. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      comments on video

      I have a few comments regarding the video:

      1. For the Explorer there is a sensor return wire for the TPS that goes to the PCM and is not connected to ground. Voltage measurements should be between the sensor signal wire and the sensor return wire instead of ground.

      2. The Explorer has no MAP.

      3. The primary sensor for measuring air flow (engine load) is the MAF sensor. The primary function of the TPS is to measure demand (accelerate, decelerate, or maintain current air flow). If the PCM determines the MAF sensor is defective the TPS becomes the primary sensor for calculating load.

      4. The typical TPS signal voltage for closed throttle is about 1.0 volts. On 2nd generation Explorers the PCM assumes the closed throttle voltage is the reading when the ignition is turned on. There is no need to adjust the TPS mounting position to achieve a specific closed throttle voltage. The PCM periodically checks for a lower minimum voltage and if found stores that as the new closed throttle voltage. For a scan tool that reads %max instead of voltage the typical closed throttle reading is 18%.

      5. Unlike a digital VOM an old style analog VOM provides a continuously updated reading and is more useful for detecting TPS dropouts.

      Have you actually tested the signal voltage using back probes? See Ford Explorer - Ranger TPS Test Procedure
       
      • Like Like x 1
    26. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      9,943
      Likes Received:
      5
      Trophy Points:
      58
      City, State:
      Greenville, SC
      Year and Model:
      00 Sport FI,03 Limited V8
      P0122

      According to the Ford OBD System Operations Summary - Model Year 1999, P0122 typically occurs when the PCM measures the TPS output voltage to be less than 0.2 volts. I suggest that you check the TPS electrical connector and wiring for functionality. You may have broken something when replacing the thermostat housing.
       

    Share This Page









    We Support Our Troops!