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Rough Idle

Discussion in 'Engine & Performance' started by ajspellm, Dec 7, 2009.

  1. ajspellm

    ajspellm Member

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    Hi,
    My 2000 Ford Expedition with the 5.4l motor has been idling really rough when its cold in the mornings. Well it has become colder here in Nebraska and I have started to notice that it is now starting to idle really rough all the time. I cant notice any hesitation because I have only had it for a couple months. I was thinking about ordering a new idle air control valve to fix it but not sure if thats totally the problem. It does not have a check engine light on either but it just idles really rough when I am at a stop light. The rpms drop three or four hundred then go up and it just idles like it has a bigger cam. It has never died but I am afraid it is going to. Any ideas on what to check first? I was going to order that new iac valve off ebay since the expedition has 123,000 miles on it and might need a new one.
    Thanks
     
  2. ELVATO

    ELVATO Super Mod Supporting Member

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    Have you tried cleaning it? What does the RPM drop to? Mine starts to shake when the RPMs approach 600. Normally stays between 650-700.
     
  3. tonydiv

    tonydiv technical advisor

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    The IAC itself won't make the truck run rough, it will only affect the idle speed. The IAC shouldn't cause a rough running condition during driving however. Coil packs are the most obvious place to start looking when the truck runs rough all the time.
     
    Last edited: Dec 9, 2009
  4. ajspellm

    ajspellm Member

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    I havent tried cleaning it. It drops to like 500 rpms or so I think. Maybe a little less but it idles really rough. It shakes pretty bad and I usually rev it up while sitting at a light. What should I look for on the coilpacs?
     
  5. JUST4FUN

    JUST4FUN Admin Staff Member

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    whats the mileage on the truck ? it might be time for a tune up
     
  6. ajspellm

    ajspellm Member

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    It just turned over to 123000 miles. I bought it from my grandparents a couple months ago and he kept up on the maintenance work religiously. I will have to ask him if he has had any problems with it idling weird and what stuff he has done to it. Its weird because it only happens when its like less than 40 degrees out.
     
  7. Lane24

    Lane24 technical advisor

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    Sounds like a vacuum leak to me. Make sure to check the elbow on the vacuum hose going into the intake at the very back of the engine near the firewall under the IAC. Betcha got a hole in it. You can stick your finger right in there, and feel a suck.

    Check this link for a better view. http://www.azda.com/ford/
     
  8. ajspellm

    ajspellm Member

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    Wow thanks for the help. That is probably it. I will have to check it when we are out of our blizzard here in Omaha lol.
     
  9. ajspellm

    ajspellm Member

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    I went to advance auto parts today and had the code checked out today and he said the code is that bank 1 is running and said I probably have a fuel injector that is plugged up. Is that code a sign the vacuum hose could be bad also?
     
  10. Lane24

    Lane24 technical advisor

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    Was it codes P0171 and P0174 . Cuz that's the code everyone I've ever talked with had before they replaced their hose, or elbow.
    The easiest way to check for a Vacuum leak is just to climb up onto your fan shroud, reach under all those hoses to the almost the back of your valve cover on the passenger side, and follow it along all the way to the firewall where it goes into the intake. ( With the engine running, so be careful) and you'll know if you have a vacuum leak. Not only can you hear it, you can feel it. It is quite a strong pull on your finger. It might even be collapsed, or cracked.
    Just have a feel before you go replacing too many O2 sensors, or IAC's or MAF's or whatever the mechanic tells you you need. It's such a common problem there is a 7 year thread running on another Ford Truck site I am a member on.

    I'm not saying this is for sure your problem, but just check it first before you go spending $$$. And make sure you have a new part before you take the old one off, cuz it will crumble in your fingers when you take it off!!!
     

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