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Discussion Starter #1
Well if I'm idling it will set a good set nice idle at like 750RPM and be smooth but if I'm driving it and im in gear at 1200RPM and i press the clutch in the rpms raise to 2000 and then 1800 and sit at 1800 untill i come to a complete stop then it idles back down.


I thought it was a vacuum leak and sprayed carb cleaner everywhere and idle never raised or did anything and i spray it on TB intake mani vaccum lines and never changed so i sprayed some all in the intake whilte reving the motor up to clean a little carbon out and when i got home the idle would bounce from 500RPM and 1800RPM and it never did this before i sprayed carb cleaner in the intake.


What could be wrong?:headscratch:
 

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I had a similar problem and it was the throttle positioning sensor. It could also be your idle air control valve though.
 
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Brake cleaner is best. Its on the side of the Throttle body when looking from the passenger fender. Front of engine side. Also check fo vac leaks. But the Symptoms your are getting are normal in a sense. But kind of excessive.

The ECM has a programmed Dashpot function, which when you go from part throttle to closed throttle, The ECM and IAC control the idle, to prevent stalling. Has to do with the VSS sensor.
 

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Discussion Starter #6
Brake cleaner is best. Its on the side of the Throttle body when looking from the passenger fender. Front of engine side. Also check fo vac leaks. But the Symptoms your are getting are normal in a sense. But kind of excessive.

The ECM has a programmed Dashpot function, which when you go from part throttle to closed throttle, The ECM and IAC control the idle, to prevent stalling. Has to do with the VSS sensor.

well, yesterday the throttle stuck, i had to turn the car off and kick the throttle pedal and start it back up. thats the first, so its either that or Idle air control valve right nothin else would do this?

and what do you mean its normal but a little excessive? do all mustang do this?
 

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Yes it is normal, refer to 89coupe's 2nd paragraph. That explains why it is doing that. He means excessive because althow it is normal, your car seems to be doing it a little more than normal or what is needed. A good cleaning of the Idle air control valve, and adjust the TPS should cure most of it if not all of it.
 

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Discussion Starter #8
wow, my buddys 5.0 automatic never did it but that cause it was on a automatic tranny and was always in gear. Well, I can drive in 5th gear at 1200 rpms and put the clutch in and it idles to 1800 untill i come to complete stop then 1000RPM.

so its got better since i flushed the coolant system. it was so nasty! the drain plug was pluged with dirty stuff!.


anyways someone school me. how do i adjust the TPS sensor and i have cleaned a IACV in my Honda so i think i know how that goes.

Also, This is not stock so some sensors are plugged dunno why? its a 70MM BBK Throttle Body though.

Thanks guys!
 

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Key on, using a digital volt meter, red lead on the green wire, and black lead on the black wire. A KOEO self test would verify that the TPS sensor is out of range. And may point to a problem with other sensors that may be contributing to this.
 

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0.98V at Idle (closed throttle) and 5.0V at WOT.
 
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