HELP! Sputtering at low RPM 99 GT -

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HELP! Sputtering at low RPM 99 GT

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Old 07-03-2013, 09:15 PM   #1
Join Date: Dec 2012
Vehicle: 1999. mustang, GT
Location: AL
Posts: 2
Default HELP! Sputtering at low RPM 99 GT

My 1999 Mustang GT starts to sputter at low rpms when heated up but when I go above 2.1k RPM it runs perfectly fine and under WOT you can feel a small amount of hesitation and then it goes full power flawlessly. I have tried everything I could. I have replaced spark plugs, inspected COP, got a brand new MAF, cleaned throttle body and air filter, and had it professionally scanned for misfires or anything and nothing at all came up. I have no idea what it could be and it is extremely annoying . My question is, is this problem common and do any of you know for sure what it could be.
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Old 07-04-2013, 12:56 PM   #2
JJ Glo
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Join Date: Mar 2013
Vehicle: 2002 Ford Mustang GT
Location: California
Posts: 91

Could be the IAC valve going bad and not being able to properly open and close to maintain a steady RPM.

My car started doing that before the IAC completely died. Perhaps the fact that I soaked it in TB cleaner helped speed up the process.

Or a vacuum leak.

Last edited by JJ Glo; 07-04-2013 at 01:29 PM.
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Old 07-04-2013, 05:33 PM   #3
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Join Date: Mar 2013
Vehicle: 98 GT 5 speed
Location: TN
Posts: 83

The fact it does it when warm suggests it could be electrically related to a sensor such as the IACV.
2006 F150, 1997 Ranger, 1998 GT
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