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Thread: My truck won't slow down

  1. #1
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    Default My truck won't slow down

    I have a 1999 Chevy Suburban with the 5.7 liter motor. When I let off the gas, the truck doesn't slow down right away, it kind of coasts as if you shifted it into neutral, and then somewhere between 3 and 10 seconds you feel the back pressure and it starts to slow. I can have the gear shift in any position, D, 3, 2, 1 and it acts this way.

    If I disconnect the Throttle Position Sensor (TPS), the issue goes away. When you let off the gas, the truck starts to slow right away, like a normal vehicle. However, running with the TPS disconnected causes bad things and so it's not a long term fix. I've replaced the TPS with a known good one and it drives the same.

    A neighbor has an identical truck and it does the same thing. His has over 200k miles and it's "..done it forever, I think since new." Mine has low miles but I haven't had it since new but it's done since I've had it.

    What's causing this and what's the fix? Dealerships tell me it's the way it's designed, nothing can be done. Some people say I need a new "chip" that will give more power and will fix it but they can't tell me why so I'm not so sure they know.

    I've searched various Chevy forums and I can't find the answer. I'm hoping someone here has direct knowledge or experience and can just give me the answer.

    Thanks
     
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    Default Re: My truck won't slow down

    Sounds a little like double clutch downshift on a manual transmission truck where you shift into neutral, match motor and transmission speed, then shift down into the lower gear. You probably have a pretty heavy duty transmission in that truck if it is meant to pull heavy loads. Could be the automatic transmission is somehow linked to the TPS to effectively create a double clutch to protect the transmission under load? Disabling the TPS might leave the transmission engaged and that's why it starts to slow immediately?

    I am really just guessing based on memory of shifting an old 3 speed manual truck and not doing it very well.
    Last edited by j44ke; 04-24-2019 at 09:46 PM.
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    Default Re: My truck won't slow down

    Is that really an issue ? On modern DSG-like equipped cars some have a setup option to coast instead of engine-brake. I sometimes put my own car to neutral when I don't need to carry more speed and don't want to engine brake. It feels a bit skateboard like.
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    Default Re: My truck won't slow down

    It probably is a design feature. It allows you to let off the gas without losing speed. It's coasting. I know some cars will 'coast' forever, well you know, till you go uphill. It should improve fuel economy.

    It's not a bad thing. If you want to slow down, use the brakes.

    If you're used to driving manuals, that's probably part of why it feels weird to you.
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    Default Re: My truck won't slow down

    Go ride a bike.
    xxoo
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