window goes down, rpm goes down car vibrates - Forums at Modded Mustangs
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post #1 of 21 Old April 14th, 2009, 11:05 PM Thread Starter
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window goes down, rpm goes down car vibrates

at a stop if i roll my window down my cars RPMS drop a little and the car kinda vibrates.. any ideas?
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post #2 of 21 Old April 14th, 2009, 11:24 PM
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post #3 of 21 Old April 14th, 2009, 11:27 PM
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Your rpms drop because of the power draw required to roll the window down. At idle, your rpms are low so when they drop even lower, you get that vibration where the engine almost wants to stall.
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post #4 of 21 Old April 14th, 2009, 11:32 PM Thread Starter
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Your rpms drop because of the power draw required to roll the window down. At idle, your rpms are low so when they drop even lower, you get that vibration where the engine almost wants to stall.

Why would it draw that much power just to roll the window down, ive drove the car a year and its always done it never causing a problem--will it in the future?
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post #5 of 21 Old April 14th, 2009, 11:33 PM Thread Starter
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Not would it, because obvioulsy no one really knows if it would but

COULD it cause a problem
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post #6 of 21 Old April 14th, 2009, 11:36 PM
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Not would it, because obvioulsy no one really knows if it would but

COULD it cause a problem
Not really. Next time your in the car turn your overhead light on and move your seat and you will notice that the light dims. Also try it with the car on and the same thing will happen.



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post #7 of 21 Old April 14th, 2009, 11:38 PM Thread Starter
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Not really. Next time your in the car turn your overhead light on and move your seat and you will notice that the light dims. Also try it with the car on and the same thing will happen.
I had a sound system in it but everytime the bass hit the lights dimmed in the interior, so i took it out.. i guess its the same concept.
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post #8 of 21 Old April 14th, 2009, 11:40 PM
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Why would it draw that much power just to roll the window down, ive drove the car a year and its always done it never causing a problem--will it in the future?
It's because your alternator doesn't provide a lot of electricity at idle. What rpms does your car idle? Mine will drop when I lower the windows, but I don't think it's ever dropped the rpms enough to shake the car.
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post #9 of 21 Old April 14th, 2009, 11:41 PM
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I had a sound system in it but everytime the bass hit the lights dimmed in the interior, so i took it out.. i guess its the same concept.
Exactly. Do you have a UDP?
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post #10 of 21 Old April 14th, 2009, 11:42 PM
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Yeah mooses is right, you need a better alternator



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post #11 of 21 Old April 14th, 2009, 11:46 PM Thread Starter
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Exactly. Do you have a UDP?

UDP??
Under Drive Pulleys?

and idles at 1250ish
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post #12 of 21 Old April 14th, 2009, 11:48 PM Thread Starter
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But that is a pure guess.. I mean it idles fine, doesnt seem high or low,. I dont think its 2grand. and its not 1k
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post #13 of 21 Old April 14th, 2009, 11:51 PM
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UDP??
Under Drive Pulleys?

and idles at 1250ish
wow. Maybe something is wrong. A 1250 rpm idle is fairly high, and shouldn't drop far enough to make your engine shake. I assumed you had an idle around 800ish, you might need to get another opinion.
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post #14 of 21 Old April 14th, 2009, 11:51 PM
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Originally Posted by Yguildl View Post
UDP??
Under Drive Pulleys?

and idles at 1250ish
Holy shit bro...why you idleing at 1250?
You should be around 720-900




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post #15 of 21 Old April 14th, 2009, 11:56 PM Thread Starter
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Holy shit bro...why you idleing at 1250?
You should be around 720-900
Like i said i have No idea, Sadly ive neve rreally paid attention to it--ill make sure i check tomorrow. i fill retarted-because i dont know, but oh well. better to ask questions and learn then to just not no at all...

i guess i dont really pay attention to things like that?


ill try to remmeber to see what my RPM at idle is tomorrow,
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post #16 of 21 Old April 16th, 2009, 10:11 PM
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Same thing happens to me. I actually just posted on a similar topic too about this.


my car idles real low and shakes my car when im at stop lights while holding down the brakes (i'm not pressing hard on them either). when i roll down the windows, i get the same effect. i have a sub woofer in the trunk, 12inch 800 watt, and hits hard, but it doesnt make the rpms drop unless i crank it so loud it hurts my ears. but with the "brakes" problem, i just put it in neutral while at stop lights and my rpms stay fine around 780-950rpm.


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post #17 of 21 Old April 17th, 2009, 03:06 AM
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Quote:
Same thing happens to me. I actually just posted on a similar topic too about this.


my car idles real low and shakes my car when im at stop lights while holding down the brakes (i'm not pressing hard on them either). when i roll down the windows, i get the same effect. i have a sub woofer in the trunk, 12inch 800 watt, and hits hard, but it doesnt make the rpms drop unless i crank it so loud it hurts my ears. but with the "brakes" problem, i just put it in neutral while at stop lights and my rpms stay fine around 780-950rpm.


GL, i hope both of our problems get solved
Sounds like run of the mill load being placed on the alternator. Wouldn't worry about it much. Do you have a capacitor hooked up to your system? That would certainly help your lights not dim as much when the bass hits.


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post #18 of 21 Old April 17th, 2009, 11:11 AM
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if your car idles at 1250 you need to check it out something is wrong vacuum leak or something


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post #19 of 21 Old April 17th, 2009, 04:07 PM
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Originally Posted by joparrett View Post
if your car idles at 1250 you need to check it out something is wrong vacuum leak or something
+1

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post #20 of 21 Old April 17th, 2009, 04:52 PM
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lol i notice the exact same thing yesterday about the lights dimming and shaking. the car itself isnt shaking its the motor that rolls the window down inside the door that is "shaking". at least i think thats what does it because only my door shakes.

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