1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Car jerks when decelerating while in gear.

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Old 07-04-11 | 06:52 PM
  #1  
DarkDrakeX's Avatar
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Car jerks when decelerating while in gear.

A few problems with things shakeing and jerking.

Say im in 5th gear and slowing down for a stop sign coming up and i leave the car in gear while braking the car jerks forward and backwards pretty bad... If i push the clutch in and brake with it out of gear it is perfectly fine.. im thinking u joints?? but i hounestly have no clue..

Also when i start off in 1st gear at low rpm my shift **** shakes back and forth pretty bad.. im assumin thats a bad transmission mount but i just wana make sure. Also when im accelerating say 2.5-3k rpm's with it in gear the shift **** shakes a little but not crazy.. enuf to make it annoying to hold onto but not like when im starting off in 1st gear..

Thanks for all the help guys.

idk if this matters but 1983 gs model 12a from a 84 gsl.
Old 07-04-11 | 07:46 PM
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Cars going to start to jutter if you leave it in gear low rpms...It wants to die. Need to rev match. Shift to lower gear.

Some symponts you can check on mazdatrix.

http://mazdatrix.com/g2.htm
Old 07-04-11 | 11:47 PM
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got emissions on it? Sounds like the shutter valve in the stock intake isny closing. Its sole purpose is to eliminate that jerking. If you pull emissions, its going to jerk around. Let me guess it jerks at about 2k rpms?
Old 07-05-11 | 01:21 AM
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DarkDrakeX's Avatar
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yeh emissions are gone. Yeh around 2k rpm.. Back when it was in my other car it didnt seem to do it i prolly wasnt paying as much attention.. cuz its pretty noticable.. thanks for the mazdatrix link.. aparently its a front ujoint.

Thanks for the help so far.
Old 07-05-11 | 03:20 AM
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All he would need to do is plug where the shutter valve was. They always go bad. Just plug it. Works better.
Old 07-05-11 | 03:23 PM
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Fighting Global Cooling

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its probably plugged now. From my experience, its always going to jerk around. Its a matter of your car hitting compression strokes at a certain rate.
Old 07-06-11 | 01:10 AM
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the actual shutter valve is plugged. So guess i cant do anything about it. Thanks for the help.
Old 07-06-11 | 09:14 AM
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A bad engine or trans mount can cause this.
Old 07-06-11 | 11:39 AM
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its supposed to do that
 
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Decelerating like that lets you experience every little bit of drive-train lash in the entire system added together.
Start with worn motor mounts, add a little worn tranny mount, throw in a weak u-joint, and just a splash of improper rear end lash. Pretty soon the car is spending its low rpm life bucking and jerking like its having an orgasm, and there you are in the drivers seat asking yourself if that "clunk," really got louder.

Urethane or hockey puck motor mounts will help, comp or urethane tranny mount will also help.

Isaac
Old 07-06-11 | 02:17 PM
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DarkDrakeX's Avatar
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Cool thanks alot flight. I was planning on hockey pucking my motor mounts ill just do it sooner than planned. Where do i get a urethane tranny mount?? Racing beat sells comp ones but just trying to see if theres any other options cuz there 70$ while stock ones are only 20 from rockauto.

Thanks
Old 07-06-11 | 05:02 PM
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flight_of_pain's Avatar
its supposed to do that
 
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In the past I have swiss-cheesed a stock tranny mount, made a form around it with tape, and filled the void with window urethane. It's not pretty but boy does it work. Any auto glass shop will sell you a tube of window urethane for a few bucks.

Isaac
Old 02-14-23 | 10:52 PM
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why are you bumping a 20+ year old thread with a link to a toyota site?
Old 02-16-23 | 09:46 PM
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That user has now been removed from the forum and all of their posts have been deleted.
Old 03-27-23 | 12:24 PM
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Car jerking when slowing down

Car jerking when slowing down is not good but you can get rid of it, if you know the reason behind it. This post help me alot to get rid of car jerking. Read Here
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