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Car Shakes When Put In Drive.


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#1
'90 Mazda 626

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Hey Guys.

I have a '90 626 DX w/automatic trans.

When I put the car in drive or stop at a light the car shakes. When I drive it is fine and if If I place it in Neutral at a stop it is also fine.

Any ideas on the problems,

#2
jiffy

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I'm not 10% sure about auto's, but if I were to guess, I would say it is a problem with the tourqe converter. Sometimes these can get a bit old and loose their pressure after time which I would imagine would present the symptoms you describe.

#3
snailman153624

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Broken motor mount.

#4
'90 Mazda 626

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Why would it only shake in Drive or reverse when sitting at a light etc....

It Does not do it in Park, Neutral or when driving.

#5
snailman153624

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Why would it only shake in Drive or reverse when sitting at a light etc....

It Does not do it in Park, Neutral or when driving.

Engine is not under load in P or N, and a worn/broken motor mount will produce a natural frequency that is very low. Correspondingly, car engines idle at low RPMs, which will be close to this natural frequency, and the engine moves around alot under the hood as a result. At higher RPMs the engine is not running near this natural frequency so you don't notice the shaking.

Either way, just LOOK at your motor/transmission mounts already :rolleyes:

#6
vlad

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It's indeed either a bad mount or the torque converter, I have also heard of autos shaking a bit when the TC gets old.

#7
river98275

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I have a 88 626 2.2L Auto Non-Turbo.

The car ran smooth through the entire RPM range, but 1-2 shift was real harsh, especially when I'd put the pedal all the way down from a stop. The car was like that since I got it (about 2 yrs ago). After 2 yrs, one day the transaxle overheated, and after letting it cool off on the roadside, it lasted about one month, then reverse went out. After another three weeks, the transaxle died altogether (car wouldn't move at all), and the fluid smelled like burnt toast.

So I acquired another transaxle (used), and torque converter. I installed those, and the car shifts real quick now, and all the gears work.

The issue I'm experiencing, is a real-rough-idle, even in Park and Neutral after installing the good transaxle and the torque converter that came with it (I left the original flexplate on the engine). If I press on the accelerater just a tad, the rough vibration goes away. I've been thinking it is a balance problem, but the new torque converter/ trans "whines" a little bit at idle, so I think the problem may be: I got a good tranny with a worn torque converter. I still have the old torque converter, and am contemplating putting it back in. The cars has 198K on it.

Any thoughts?

#8
Blind Freddie

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most of the time the rough idle is brought on by the ripped throttle boot (black hose between throttle body and air flow meeter), pull it off inspect for cracks and replace as unnecessary. they are usual items that go on these cars and in autos with bad mounts are especially noticeable

if that is fine, you mounts could be ABSOLUTELY shot, but then generally you should feel and/or hear knocking from the engine bay as you shift R-N-D-N-R

How is your idle? is it set right? Drive range puts load on the engine and hence low idle is very noticeable

i would put my focus on finding vacuum leaks first.

#9
sdimick

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What is the factory idle speed for the auto 626 n/a 2.2? Im having the same issues, no vacuum leaks.

#10
aleekat

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Is the idle air control valve "cleanable" on this model? Have a later 626 that had the same symptoms. Couple tamper proof "star" screws. Pulled the valve, carbon, dirty etc. Cleaned it up and all is well.

#11
fatmatt86

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Easy way to see if they are the motor mounts is to get a jack and a block of wood and place them under your oil pan and jack the engine up. Start your car and if it doesn't shake it is definitely the motor mount. Just changed mine 2 days ago, because I had the same shaking problems. After I changed them my car ran smoothly and no shaking at all.




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