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2001 Ford F-150 intermittent rough idle

Tiny
SUPERCREWCAB
  • MEMBER
  • 2001 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 90,000 MILES
I have a 2001 Ford F150 Supercrewcab 4X4 with an intermittent idle problem. Seems to only do it when the truck is in drive and only once in awhile. It will idle down too low then recover usually. It actually died on my wife yesterday, which was scary. When in park it seems to idle fine and I don't detect any misses or issues when driving down the road.

No codes are set and the check engine light does not come on. I'm suspecting the IAC or something related to that area.
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Wednesday, December 16th, 2009 AT 10:34 AM

11 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Could be an IAC, have you tried cleaning the throttle body and IAC, check it for carbon deposit holding the pintle from free movement. When was your last tune up? MAF can also do this, unplug it MAF and test drive it. This will set a code, but if it is the MAF, the PCM will sub mid range numbers to run the engine.
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Thursday, December 17th, 2009 AT 2:58 AM
Tiny
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I checked the IAC yesterday. Pulled it off checked voltage input per manual, checked good. Checked the IACs resistances all check good. Looked for obvious carbon build etc. Didn't see much.

My wife drove it yesterday after I did the above and said the RPMs never dipped below 600, so maybe it was just dirty connection.

I'm going to check the Throttle body for carbon build-up anyway and the line going from the PCV valve to TB.

Then the MAF.

Thanks
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Thursday, December 17th, 2009 AT 12:01 PM
Tiny
MERLIN2021
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OK Let us know how it goes!
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Saturday, December 19th, 2009 AT 2:10 PM
Tiny
SUPERCREWCAB
  • MEMBER
  • 5 POSTS
Since I took the IAC valve and cleaned it, the truck has been idling dead on, so I'm not going to mess with it anymore. We're driving up to Shelton, Wa on Monday from SoCal that should test it out pretty well.
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Saturday, December 19th, 2009 AT 5:31 PM
Tiny
MERLIN2021
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Ok, give us an update!
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Thursday, December 24th, 2009 AT 7:06 AM
Tiny
SUPERCREWCAB
  • MEMBER
  • 5 POSTS
Okay, We made the trip to Washington. The idle fluctated on the last day of our visit (27* outside). We hit the road and she ran fine all the way home with no further idling problems. I've gone ahead and changed the IAC valve and will see if the problem clears. Due to the intermitancy of it, it'll be a while before I'm sure it's good. I figure the IAC valve was sticking causing the fluctuations. I don't think it's vacuum related because I'd see the problem more consistantly.

IAC Valve was $50.00, so not too expensive to try.

I'll provide an update in a few days.
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Wednesday, December 30th, 2009 AT 4:35 PM
Tiny
MERLIN2021
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Ok I'll be here!
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Wednesday, December 30th, 2009 AT 5:18 PM
Tiny
SUPERCREWCAB
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  • 5 POSTS
Well, it's been over a week now and the truck is running perfect so I would say it was the AIC valve. Thanks for the help.
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Monday, January 11th, 2010 AT 9:56 AM
Tiny
MERLIN2021
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Good work, thanks!
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Monday, January 11th, 2010 AT 1:37 PM
Tiny
SPORTSFAN
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I just came across this post -- I have a 2000 f150 supercab 4x4 with 5.4 motor w/ 131K miles. I live in MA. I have been having an issue where when I pull up to a stop sign or a red light the idle will be rough and it will feel like it wants to stall but doesn't. This happens everyonce in a while. Once I start moving it goes away. It seems to be fine in park. I recently had my alternator and battery replaced and the issue has been occuring on since then (4 weeks ago). The next day after the alternator was replaced the check engine light came on -- the garage checked it and it read Lean Bank 1 and Lean Bank 2 - both indicators of the MAF sensor. They reset the code and it has not tripped the check engine light since. Could it be the MAF? Also, the plugs and coil paks were changed about a year ago.

I appreciate any feedback that you may have.
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Thursday, January 14th, 2010 AT 10:16 AM
Tiny
MERLIN2021
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Get a can of spray Throttle body cleaner, start the car and spray around, pay attention to vacuum lines and manifold, if the idle changes, you found a leak. You want the engine running and spray on the outside but do direct the stream onto the hoses, On trucks with a plastic upper intake, spray around the seams, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs!

The other possibilty is the idle air control, it, s bolted to the side of the throttle body.
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Thursday, January 14th, 2010 AT 12:43 PM

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