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RPM’s dropping off after steady speed

  • Thread starter Thread starter Greg Smith
  • Start date Start date Jul 20, 2025
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Greg Smith

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#1
  • Jul 20, 2025
  • #1
After a sustained highway drive, if I simply kick the car out of gear and coast up an offramp, the RPMs fluctuate and drop very low until the car will die. If I run it down through the gears while going up the ramp, it’s fine. 2007GTCS, six speed trans.
 

Noobz347

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#2
  • Jul 20, 2025
  • #2
IAC
 
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Greg Smith

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#3
  • Jul 21, 2025
  • #3
Well, I wasn’t aware the 2007 to 2009 had an IAC. . Thanks.
 

Noobz347

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Me either, one way or the other.
 

Noobz347

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Have you pulled codes (regardless of whether the light is on or not)?
 

Dino Dino Bambino

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#6
  • Jul 22, 2025
  • #6
Greg Smith said:
After a sustained highway drive, if I simply kick the car out of gear and coast up an offramp, the RPMs fluctuate and drop very low until the car will die. If I run it down through the gears while going up the ramp, it’s fine. 2007GTCS, six speed trans.
Click to expand...

The inside of the throttle body between the blades and the bores may have enough dirt deposits to restrict airflow when the throttle is closed. Remove the TB and clean it thoroughly.
 
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Greg Smith

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Nov 26, 2017
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Jul 22, 2025
#7
  • Jul 22, 2025
  • #7
Noobz347 said:
Have you pulled codes (regardless of whether the light is on or not)?
Click to expand...
Yes, no codes pending or active.
 
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