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Automatic downshift question

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Old Feb 16, 2012 | 11:35 AM
  #1  
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From: Edmond OK
Default Automatic downshift question

At highway speeds my C4 wont downshift at say 70 mph if i floor it, it just wants to stay in OD like it is one long gear. Is this normal or shouldnt it drop down into drive (3rd)?
Car also runs lean under heavy throttle and when i give it 100% throttle it only shows 65% output. I have replaced the plug wires, plugs, and done a smoke test for vacuum leaks
but it was doing this same thing before i did all of that. Any takers?

Last edited by scottermis; Feb 16, 2012 at 12:08 PM.
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Old Feb 16, 2012 | 12:44 PM
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What year/trans did you say it is again?
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Old Feb 16, 2012 | 01:11 PM
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Sounds like a TPS (throttle position sensor). If the PCM is only seeing 65% throttle it doesn't think it needs to downshift. Try resetting it first.
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Old Feb 16, 2012 | 05:00 PM
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Well i found the issue and am a bit embarrassed. There is a plastic adjustor on the ASR cable box that lets you adjust how much throttle you are pushing. After a quick adjustment i can get 100% and alli can say now is WOW! This is my first Vette and since i have had it i have been running it at about 65% throttle. I bought this car from a younger guy whose grandfather gave him the car and i bet he had it adjusted that way. I am gonna get a ticket for sure now.....lol
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Old Feb 17, 2012 | 01:59 AM
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Tickets are good

Accidents, not so good

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Old Feb 17, 2012 | 11:08 AM
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Wow, a 100hp mod for $00. Can't beat that.
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