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I own a 2003 Ford Ranger Edge with the 4.0 engine. A couple ...

Customer Question

I own a 2003 Ford Ranger Edge with the 4.0 engine. A couple of weeks ago my idle speed dropped and it died. First time since I bought it new. It restarted and was idling too slow. I revved the motor a couple of times and realized it was missing at high RPM''s and the tach will not go over 3,000 rpm. That''s where it starts runnung rough and no RPM increas at idle. No loss of power when driving. I''m wondering if there is a built-in governor so high RPM idling is prevented or if I have a real problem ???
Submitted: 8 years ago.
Category: Ford
Expert:  RIP replied 8 years ago.

Hi, welcome to Just Answer.

  1. How many miles are on this Ranger?
  2. Has the check engine lamp illuminated since the problem(s) began?


Customer: replied 8 years ago.
1. 55,000 miles
2. No , the check engine light has never come on.
Expert:  RIP replied 8 years ago.

Thanks, XXXXX XXXXX like a common problem with the IAC (Idle Air Control) valve. These valves become gummed from age and cause a low idle, rough idle, and intermittant stalling. The IAC is correctly tested through a factory level scan tool, but for the cost of a new valve and the ease of replacement; I recommend you replace it along with a good cleaning of the throtle body and see if the problem still persists. Below is the procedure to replace the valve. Most auto parts stores carry these in stock as well.

Service and Repair



  • Remove the accelerator control snow shield.


    1. Disconnect the electrical connector. Remove the bolts and the Idle Air Control (IAC) valve.


    1. To install, reverse the removal procedure. NOTE: Install a new IAC gasket.


    Customer: replied 8 years ago.
    1. Would the IAC valve cause a miss at 3,000 RPM or higher if it is malfunctioning?

    2. What should I use to do a good cleaning of the throttle body & how?
    Expert:  RIP replied 8 years ago.

    An IAC valve failure commonly does not cause an actual missfire, but it can cause a hesitation or feeling of a missfire. You may have two seperate issues going on here, but I would get the IAC out of the way and see if this missfire remains. Typically an engine missfire will almost immedialty cause the check engine lamp to flash and set illuminated.

    For the throtle body cleaning, you can simply purchase good throtle body cleaner (not carburator cleaner) from a local parts store. Remove the air intake duct at the throtle body and hold the throtle open. Use a rag and wet it down with cleaner. Using the wet rag swab down the inside if the throtle body and around the plate as well. Once you get the accumilated carbon off the throtle bore and throtle plate, you can rinse down the inside by spraing it. However, you want to be carefull to not use too much cleaner,it can flood the engine which leaves a chance for damaging it. You should be able to get all of the carbon buildup off, and see a very clean throtle bore. After replacing the IAC and cleaning the throtle, remove the battery cables for about 10 minutes to reset the enigne's computer idle strategy. Than fire up the engine and let it idle for about 10 minutes. If this missfire at higher rpm's remains, let me know....and we'll take it from there.


    Customer: replied 8 years ago.
    I am not yet persuaded to spend $80 to buy a new IAC vave to determine if this is going to correct the problem. However, I called my local auto parts dealer today. They did not have one in stock, but gave me a price to order one. I read that the IAC valve can be cleaned fairly simply. I also read that this condition may be caused by an incorrect ground circuit in the electrical distribution (EDIS) module connector. Also, an injector cleaning may clear up the problem. I prefer to take the less expensive & labor intense options first.
    Expert:  RIP replied 8 years ago.
    No problem....but when you do find you need an IAC valve, please be fair and press the ACCEPT button for the help, and remember that cleaning the IAC is only a temporary solution - if that. Thanks.
    Customer: replied 8 years ago.
    I think I need to clarify my problem. Your recommendation is to replace the IAC and clean the throttle body. I don't have an idle problem. The motor has only slowed and died on one occasion since I have owned the vehicle. The problem is the motor stalls/misses when it reaches 3,000 RPM's and will not turn any faster. Please tell me again if you still think that this is caused by a problem with the Idle Air Control valve.
    Customer: replied 8 years ago.
    Please reply to my last inquiry. I am trying to make sure I have clarified the nature of my problem. If you still think I need to purchase a new IAC valve, then I will do so ASAP.
    Expert:  RIP replied 8 years ago.

    In your original question you stated that the idle speed dropped and the engine stalled. Than you restarted it and the engine idles low. Those symptoms correspond to a faulty IAC valve. An IAC can also cause it to not rev, but that is much more rare and usually sets the check engine lamp. The missfire your feeling at higher rpm's is NOT an indication of an IAC failure, however, most missfires or hesissitation on this truck will cause the check enigne lamp to flash or illuminate. I would replace the IAC first as well as clean the throtle body; and see if both problems are gone or one still exists. The MAF (Mass Airflow Sensor) on these is also a prone failure and I believe you may have a combination of a dirty MAF sensor and a faulty IAC valve...if you had access to a factory level scan tool both of those components could be tested.


    Customer: replied 8 years ago.
    Well RIP, I finally solved my problem. See below

    Expert: Dennis W
    Date: 10/21/2007
    Subject: Ford Ranger Engine

    Question [Asked by someone else]
    My Ford Ranger 4.0L automatic 36000 miles will not rev over 3200 RPM. Engine operates normally up to 3200 RPM then surges approx 100-200 RPM at 1-2 second cycles with a distinct rocking (out of balance), this quickens with increased accelerator pressure. The problem occurs without a load (revving in neutral)- the check engine light is not on.

    This is normal if you are revving the engine in park or neutral, the PCM has a rev limiter to prevent engine damage. If the symptom occurs while driving you might have a problem with the MAF sensor or fuel pressure. Check for codes BEFORE making or attempting any repairs.


    In my original question I wrote: "I'm wondering if there is a built-in governor so high RPM idling is prevented or if I have a real problem ???"

    Then later I wrote: "The problem is the motor stalls/misses when it reaches 3,000 RPM's and will not turn any faster."

    I could not have made this any clearer. It does not occur while driving and the idle fluctuation only happened the one time and never since. Obviously, I have no need for any parts or any repairs. Perhaps if this comes up again, you will know how to respond correctly without recommending unnecessary parts or unneeded service repair.
    Expert:  RIP replied 8 years ago.

    Listen you said the motor stalled on you, with those symptoms...you'll eventually need an IAC valve, even one stall is not a normal condition. The engine does not rev in park, but it is NOT supposed to missfire so either you just thought it was a missfire when it reached it's rev limit, or there is an actual problem. I gave you my opinion with the symptoms you provided; take it whichever way you like.


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