| Author |
Message |
Isaiah Beard
Guest
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 Posted:
Mon Jan 17, 2005 7:51 am Post subject:
Coast in Neutral + brake to slow down = HUGE SLAM? |
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I've noticed some interesting (at best) behavior on my 2002 Grand Am SE,
2.2L ECOTEC 4-cyl engine when coasting in neutral.
I recently moved into a house in a semi-ruralish, not-yet-developed (and
hope it stays that way) area with extremely little traffic, at the
bottom of a hill. Driving home, I get off the main highway, which runs
along the top of this hill. I discovered that if I put the car in
neutral, I can just coast this way with the momentum keeping me at about
35 MPH (which happens to be the speed limit), having only to apply the
brakes lightly at the end when it's time to pull in and park.
However, I noticed that frequently, but not all the time, the car will
slow down smoothly as I apply the brake, only to LURCH forward HARD
right at the moment the speed of the car drops below 10 MPH. It feels a
lot like a 100-pound weight or so has suddenly shifted forward in the
engine compartment and hit the front of the frame, stopping hard.
However the car will never do this if I leave the gear in Drive and
similarly coast (though I then find that I have to tap the brake on
occasion to keep me at or below 35 MPH).
I had thought it might be something peculiar with the car, perhaps
faulty engine mounts, but lo and behold, I discovered that my 2004 Chevy
Cavalier, with the same 2.2L Ecotec engine (but I don't think it's the
same transmission, not sure) exhibits the EXACT same behavior.
Also I recently had the opportunity to rent a 2005 Chevy Trailblazer,
and for grins, I tried the coast with it. It did NOT lurch when I
coasted in neutral. It has the Vortec 4200 Inline 6 engine, though, and
is signifcantly heavier.
Anyone know what's causing the lurch? The cars don't seem to be any
worse for wear, but I've stopped doing the Neutral coast, just in case.
--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply.
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Professor
Guest
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| Posted:
Mon Jan 17, 2005 6:11 pm Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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I got a hunch it's a brake thing. You're on you brak more when in gear,
but only touch up at about 10mph when in neutral. Both your cars can't
have loose calipers though. Try coasting right by without hitting the
brake. Or try riding the brake slightly from the top like when in
drive.
Hey, maybe your seats are loose. |
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Terry
Guest
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| Posted:
Mon Jan 17, 2005 10:11 pm Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Isaiah Beard wrote:
| Quote: |
I've noticed some interesting (at best) behavior on my 2002 Grand Am SE,
2.2L ECOTEC 4-cyl engine when coasting in neutral.
I discovered that if I put the car in
neutral, I can just coast this way with the momentum keeping me at about
35 MPH (which happens to be the speed limit), having only to apply the
brakes lightly at the end when it's time to pull in and park.
However, I noticed that frequently, but not all the time, the car will
slow down smoothly as I apply the brake, only to LURCH forward HARD
right at the moment the speed of the car drops below 10 MPH.
Anyone know what's causing the lurch?
|
Does the car have anti-lock brakes? My car sometimes has a pulseing at 10
m.p.h. and this feels as if the brakes "let go"
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Woody
Guest
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| Posted:
Mon Jan 17, 2005 11:14 pm Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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You aren't generating enough vacuum at idle to overcome the loss in the
brake booster. Ala no power brakes.
"Isaiah Beard" <sacredpoet@sacredpoet.com> wrote in message
news:10umhnt7ds72i15@corp.supernews.com...
| Quote: |
I've noticed some interesting (at best) behavior on my 2002 Grand Am SE,
2.2L ECOTEC 4-cyl engine when coasting in neutral.
I recently moved into a house in a semi-ruralish, not-yet-developed (and
hope it stays that way) area with extremely little traffic, at the bottom
of a hill. Driving home, I get off the main highway, which runs along the
top of this hill. I discovered that if I put the car in neutral, I can
just coast this way with the momentum keeping me at about 35 MPH (which
happens to be the speed limit), having only to apply the brakes lightly at
the end when it's time to pull in and park.
However, I noticed that frequently, but not all the time, the car will
slow down smoothly as I apply the brake, only to LURCH forward HARD right
at the moment the speed of the car drops below 10 MPH. It feels a lot
like a 100-pound weight or so has suddenly shifted forward in the engine
compartment and hit the front of the frame, stopping hard. However the car
will never do this if I leave the gear in Drive and similarly coast
(though I then find that I have to tap the brake on occasion to keep me at
or below 35 MPH).
I had thought it might be something peculiar with the car, perhaps faulty
engine mounts, but lo and behold, I discovered that my 2004 Chevy
Cavalier, with the same 2.2L Ecotec engine (but I don't think it's the
same transmission, not sure) exhibits the EXACT same behavior.
Also I recently had the opportunity to rent a 2005 Chevy Trailblazer, and
for grins, I tried the coast with it. It did NOT lurch when I coasted in
neutral. It has the Vortec 4200 Inline 6 engine, though, and is
signifcantly heavier.
Anyone know what's causing the lurch? The cars don't seem to be any worse
for wear, but I've stopped doing the Neutral coast, just in case.
--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply. |
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Isaiah Beard
Guest
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| Posted:
Tue Jan 18, 2005 3:37 am Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Professor wrote:
| Quote: | I got a hunch it's a brake thing. You're on you brak more when in gear,
but only touch up at about 10mph when in neutral. Both your cars can't
have loose calipers though. Try coasting right by without hitting the
brake.
|
Actually I have tried this as well to rule out the brakes. The car
still lurches/slams forward as it approaches 10MPH.
--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply. |
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Isaiah Beard
Guest
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| Posted:
Tue Jan 18, 2005 3:39 am Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Terry wrote:
| Quote: | However, I noticed that frequently, but not all the time, the car will
slow down smoothly as I apply the brake, only to LURCH forward HARD
right at the moment the speed of the car drops below 10 MPH.
Anyone know what's causing the lurch?
Does the car have anti-lock brakes? My car sometimes has a pulseing at 10
m.p.h. and this feels as if the brakes "let go"
|
The Grand Am does, but the Cavalier does not. Also the Grand Am has
traction control, but not the Cavalier. I just find it odd that the two
cars would do the same thing. The only common thing between the two of
them is they're both FWD, and they have the same type of engine.
--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply. |
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Ken Weitzel
Guest
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| Posted:
Tue Jan 18, 2005 4:21 am Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Isaiah Beard wrote:
| Quote: | Terry wrote:
However, I noticed that frequently, but not all the time, the car will
slow down smoothly as I apply the brake, only to LURCH forward HARD
right at the moment the speed of the car drops below 10 MPH. Anyone
know what's causing the lurch?
Does the car have anti-lock brakes? My car sometimes has a pulseing
at 10
m.p.h. and this feels as if the brakes "let go"
The Grand Am does, but the Cavalier does not. Also the Grand Am has
traction control, but not the Cavalier. I just find it odd that the two
cars would do the same thing. The only common thing between the two of
them is they're both FWD, and they have the same type of engine.
|
Hi...
Wondering if they were in overdrive, and just coasting, if
that isn't the point that the convertors unlocked ?
Ken |
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Isaiah Beard
Guest
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| Posted:
Wed Jan 19, 2005 12:37 am Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Ken Weitzel wrote:
| Quote: | The Grand Am does, but the Cavalier does not. Also the Grand Am has
traction control, but not the Cavalier. I just find it odd that the
two cars would do the same thing. The only common thing between the
two of them is they're both FWD, and they have the same type of engine.
Hi...
Wondering if they were in overdrive, and just coasting, if
that isn't the point that the convertors unlocked ?
|
Well see, taht's the thing. This only happens when the car coasts in
neutral. When I coast downhill in overdrive, it's smooth all the way to
the end.
--
E-mail fudged to thwart spammers.
Transpose the c's and a's in my e-mail address to reply. |
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Sportster4Eva
Guest
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| Posted:
Wed Jan 19, 2005 8:41 pm Post subject:
Re: Coast in Neutral + brake to slow down = HUGE SLAM? |
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Woody wrote:
| Quote: | You aren't generating enough vacuum at idle to overcome the loss in the
brake booster. Ala no power brakes.
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Vacuum is high at idle, low on acceleration <sp>, and highest on
coasting in gear (engine braking).
It's probably the converter clutch releasing.
Coasting in N is something most people don't do, and possibly the tranny
/computer doesn't know how to properly deal with it..
$.02
--
Paul
'91 XL1200
'77 GL1000 (W.I.P.)
"I feel more like I do now than when I got here" |
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