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Idle rpms go up then drop back down over and over

  • Thread starter Thread starter Drachnem
  • Start date Start date Dec 14, 2008
D

Drachnem

New Member
Dec 5, 2008
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Dec 14, 2008
#1
  • Dec 14, 2008
  • #1
I just bought this mustang and I'm not huge into mechanics so maybe you guys can help me out.

My mustang when Idle after a few mins starts to go up in rpm then back down over and over.

What is doing this and how can I fix it?
 
K

Kampfer03

New Member
Dec 31, 2008
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Dec 31, 2008
#2
  • Dec 31, 2008
  • #2
It could possibly be the idle pulley.
I had the same problem on my 98.
 

Ogre

Active Member
Sep 24, 2003
120
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NC
Dec 31, 2008
#3
  • Dec 31, 2008
  • #3
I would look at your throttle position sensor (TPS) or idle air control valve (IAC). I had a 94 coupe that when started up when cold, it would idle up to around 2000 rpm then slowly idle down to around 700 rpm, where it should be. Also, driving it down the street it was like the cruise control was set to 35 mph.

I changed out the IAC, and was good to go.
 
D

Drachnem

New Member
Dec 5, 2008
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Jan 1, 2009
#4
  • Jan 1, 2009
  • #4
I cleaned out the IAC and let it idle for about 10 mins, then blasted the heat while going from park to drive seems to have done the trick, I haven't got the chance to take it for a road test yet either. I also cleaned the MAS
 
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