Resolved High idle when warmed up that slowly comes down over 2-5 seconds...

NooStang

Member
Mar 15, 2024
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When the car ('87 GT) is at operating temp and I let off the gas pedal the idle can go past 2000rpm then slowly come down about 2-5 seconds after letting off the accelerator pedal. This does not happen at all until the car is at operating temp and slowly worsens the more I drive the car. Also, if I change gears at 1500 RPM the engine speed can sometimes increase to 2200RPM. If I hold the clutch down while leaving the gas pedal alone during gear change the engine RPM will come down over 2-5 seconds. I checked to make sure this is not a sticking pedal/cable, it is not.

Cold idle is set to around 800RPM.

Is there an issues with TPS sensors causing these symptoms when the engine is warmed up?

If I shut the car off and restart at the stop light, the problem is fixed for a very brief period of time.

Anyone have a suggestion on a possible culprit? Thanks for any help.
 
Last edited:
+1 on checking for codes but I suspect it likely may be a procedure issue, need to set the idle on the engine when at operating temp. Including a computer reset.
And, as suggested check for vacuum leaks.