idle help -

4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

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Old 03-10-2016, 03:29 PM   #1
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Default idle help

hello i could use your help figuring out my idle issue, my rpms drop down every 8+/- secs and lasts about 12+/- secs. i have talked to some people who think it might be my idle air valve, but a new symptom has occurred that is throwing me for a loop, it is now squeaking at the same time, the squeaking gets gradually louder over the 12 secs then stops completely for 8 and so on. so rpms drop and squeaking, any ideas? F.Y.I squeaking sounds like the belt area not up at the valve, this is why i ask... is offline   Reply With Quote
Old 03-10-2016, 04:02 PM   #2
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Does this idle condition coincide with having the hvac settings on either A/C or Defroster?

Every time the compressor cycles on and off it places/reduces load on the engine and under those circumstances a slight fluctuation in idle speed is normal. The squeaking would likely be the serpentine belt, and could be due to either the belt itself needing replacement or the tensioner pulley is faulty.
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Old 03-10-2016, 04:16 PM   #3
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i did have the air on but not the A/C, but i did notice a good amount of condensation build up on the A/C lines under the hood which i thought was weird since the A/C was off? Also the belt is pretty new and looks in good condition and if the pulley was going bad wouldn't the squeaking be a pretty continuous thing? it only squeaks when rpms drop... is offline   Reply With Quote
Old 03-10-2016, 04:56 PM   #4
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IAC or vacuum leak
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Old 03-10-2016, 05:08 PM   #5
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any tips to troubleshooting that? is offline   Reply With Quote
Old 03-11-2016, 08:02 AM   #6
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Sounds like you had the defrost selected, selecting defrost turns the AC compressor on and off in intervals. This is to ensure that during winter months the compressor doesn't seize up from not being used.

The squeaking is most likely due to needing a new belt or it may be have a little moisture on it , it squeaks when the extra load of the compressor is kicked on.

FYI,,, my 00 gt idle will do the same thing when the defrost is selected, minus the squeaking.
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