The infamous silent deceleration - Ford Powerstroke Diesel Forum
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Old 04-21-2008, 08:49 PM
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The infamous silent deceleration

Ok. I hope all your rigs do this, of similar years ect. While going steady at a medium to high rate of speed say 55 or 70. Cruise on or not, and you just let off. Everything goes quiet, as if the engine stalled. The tach still reads, EVERYTHING functions normally, but I hear no injectors or combustion at all. Until maybe 1500-1700rpms. And if going say 55 or whatever and slow down very quickly the injectors/combustion goes intermittently until 1400 and down to 600 or so rpms. It also does it while going slow like 35 and let off again until the rpms drop to say 1400.

What is that?! I think it is friggin awesome but I don't understand it 100%. I understand engine braking but are the injectors actually "turning off"? And if so does the engine keep running just on compression/centrifugal force? How's it work. Also if it is shutting injectors down, cutting them off whatever to make them not inject does it do that to all 8 or is it the miraculous "cut off 4 cylinders for economy" type of thing like all the new gasser SUV's and trucks. One more thing, this "coasting" effect, is that what the COAST button on the steering wheel does?

PLEASE someone explain this to me.
I just want to know how this system works, it's very fascinating. And I just can't figure out HOW it works, and what it's SURELY doing.
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Old 04-21-2008, 09:04 PM
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I know exactly what you're talking about. Always kind of wondered about that when I had my 99.
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Old 04-21-2008, 09:08 PM
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Quote:
Originally Posted by 99Smokin73Stroker View Post
I know exactly what you're talking about. Always kind of wondered about that when I had my 99.
Glad you are understanding my lengthy description there. Its so weird. I hate not knowing what's going on...
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Old 04-21-2008, 09:09 PM
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All the 7.3 SD's I drive do this. The coast button on the steering wheel is for the cruise control. Go and drive the truck turn cruise on and then after it sets press and hold the coast and the truck will slow down. Press and hold the set/accel button and the truck will speed up. When you step on the brakes and turn CC off press res and it will turn back on.
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Old 04-21-2008, 09:12 PM
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Originally Posted by 2005F250 View Post
All the 7.3 SD's I drive do this. The coast button on the steering wheel is for the cruise control. Go and drive the truck turn cruise on and then after it sets press and hold the coast and the truck will slow down. Press and hold the set/accel button and the truck will speed up. When you step on the brakes and turn CC off press res and it will turn back on.
So it is coasting. I thought so. Just doing that would duplicate what I was saying with the different speeds and rpm controlled by Mr. Right Foot.

That answers one question, now why and more importantly how is what I'm wondering.
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Old 04-21-2008, 09:14 PM
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Originally Posted by 2005F250 View Post
All the 7.3 SD's I drive do this. The coast button on the steering wheel is for the cruise control. Go and drive the truck turn cruise on and then after it sets press and hold the coast and the truck will slow down. Press and hold the set/accel button and the truck will speed up. When you step on the brakes and turn CC off press res and it will turn back on.
Oh and thank you for sure. You not only answered one question but gave me a much better understanding of how to work the cruise on it. I got how to set it and shut it off LOL. It's alot different than the ole Buick.
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Old 04-22-2008, 05:55 AM
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Nobody knows? Really? Over 40 views and only two people wanna say something, whats up with that?
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Old 04-22-2008, 06:07 AM
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You know what's funny is that a guy on DTR posted in a thread I'm subscribed to about the exact same type of thing sometime last night or early this morning. lol.....
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Old 04-22-2008, 06:18 AM
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Originally Posted by 99Smokin73Stroker View Post
You know what's funny is that a guy on DTR posted in a thread I'm subscribed to about the exact same type of thing sometime last night or early this morning. lol.....
Wow that IS weird. Great minds think alike! What did he find out? Anybody on there know?
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Old 04-22-2008, 06:36 AM
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so is this a automatic or a stick? I would assume if it's an automatic that the torque converter has just disengaged and the truck is coasting at idle..my '06 SD does the same thing..lightly touch the accel and it comes back to life and pulls fine-it's just a coast mode as I see it...with fuel getting to be $4+ a gallon,just sit back and enjoy.
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