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Discussion Starter #1 (Edited)
While driving slow, turning or taking off even stopping the car keeps stalling and then the dash message shows "speed limited to 140" I am not speeding or driving fast I am actually only doing 10 mph or idling. The car doesn't stall when driving fast. There are no codes or dash lights except a code for the brake pedal when checked by local car part store computer.
Its a 2007 impala v6 3.9L police with 225k miles.

Can anyone tell me what to check next? I am thinking maybe tps sensor or ecm next? I have replaced the speed sensor.


The ac also cuts off sometimes and blows hot air and when i push the power window up or down button it seems like the there might be a power issue because the ac seems to act like it wants to cut off when i roll the window up or down. I dont know if this is related or means anything but i thought I would mention it.

I replaced the speed sensor, water pump, oil pressure sensor, idle pully, spark plugs, fuel injection has been cleaned, throttle body has been cleaned, mass air flow sensor has been cleaned, oil change radiator flush, new drive belt, fixed o2 sensor rear exhaust and exhaust pipe damage. Just trying to be thorough.
 

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Sounds to me like you are on the right track with the speed sensor. Somehow the computer is getting a message of your speed being too high so it cuts power to the engine. Does the speedometer also peg to 140 when this happen? Did you change the output shaft speed sensor? If so, I would trace that wire and see if it has a break or short in it somewhere. May even try another sensor just to be sure. If you can't find anything there, I suppose it could be ECM related, but I would think you would have other problems too.

As for the a/c window...that is strange. My only thought is that for some reason maybe you don't have enough voltage/current coming from your charging system to do both. When you use your window motor, you don't have enough power to keep the a/c clutch energized maybe? It may not be a bad idea to have your battery and alternator tested.
 

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when you said 140 mph i couldnt help but remember on my 95 SS with this sticker
 

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Discussion Starter #4
Hi, Yes the speedometer does twitch or bounce whether I am stopped or driving 10mph. The car also has a really rough cold start in the am sometimes.I'm in Florida so it's warm otherwise. The car does run much better in park then drive. I replaced the speed sensor is there more than one?
 

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Discussion Starter #5
Sometimes when it is trying to stall the speedometer will bounce up and down like crazy and when I get the speed limited to 140 message it usually has died really fast before I can see the speedometer.
 

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Based on looking at rockauto and the parts available, it has a transmission input shaft sensor, and an output shaft sensor. I would have to imagine the output shaft sensor is where the actual speed comes from. That would be the one I would be looking at the wiring for or possibly replacing again if it hasn't already been replaced.
 
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