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car shake violently at traffic light

1991 Honda Civic, automatic transmission, the car/steering wheel shake badly when the car stops at the red light. It only happens when brake pedal is pressed AND in D gear. If shift from D to N, the shake disappears. As soon as the traffic light turns green and the car starts to accelerate, the shake disappears. Four spark plugs were replaced, no effect at all. Thanks for your help.
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Comments

  • edited February 2011
    You have a failed motor mount. Pretty cheap repair for your car, maybe $100 max.
  • edited February 2011
    Thanks for the reply. If engine mount is bad, shouldn't the car shake all the time. It only shakes when stops in traffic light and only in gear. Shifting to neutral then shake is gone.
  • edited February 2011
    kizwiki's guess is certainly possible but it is just a guess.

    What you have to wrap your head around is that putting the car in gear puts load on the drivetrain. It is that load that is leading to the shaking.

    This might happen because of a bad motor mount.

    It will also happen for 100 other reasons that no one can guess about because you haven't said anything else about the car. Most of these reasons have to do with simple things like spark plugs - so now that you've gotten that far do the rest. New wires, new air and fuel filters. A check for vacuum leaks and a check of the fuel pressure would be in order.

    Basically, rather than guessing first at a motor mount I'd guess first at your car not running right.
  • edited February 2011
    I guess it might be to do with the fuel system and idle speed because when the traffic light turns green, I apply the gas pedal (it certainly puts load on the drivetrain) then the shake is gone and the engine is quiet. Perhaps not enough air/fuel mix at idle while in gear (load on engine) causes the shake?
  • edited February 2011
    Something wrong with the air/fuel mix (thus do air & fuel filters, check fuel pressure and for vacuum leaks) or something wrong with spark (thus have a look at the spark plug wires). But a look at the motor mounts is also in order. If nothing turns up there then you move on to other things (like distributor/coil, EGR system...)

    Is the check engine light on?
  • edited February 2011
    The check engine light was one a few times duel to misfire (I guess since Autozone can't read code for older cars). After I replaced the spark plugs, the engine light was still on a few times. After I pour some fuel injector cleaning liquid to gas tank, the light is no longer on anymore so far. This engine light problem was only in the past few months. However, I don't feel it is related to the engine shake because this shake problem has been there for many years. Air filter was replaced and is clean. I didn't check fuel filter recently but it was replaced in 2003 and I think should be fine as well. Well, the problem is I really don't want to put more money in this old car so as long as it runs fine I guess this minor shake issue is tolerable to me. I was just puzzled/curious what causes the problems though.
  • edited February 2011
    The mounts can be diagnosed using a floor jack. Have an assistant run car in gear with foot on brake. Use floor jack to jack engine up slightly to get the weight off the mount. If this helps, then it's a mount.
  • edited February 2011
    Is There An Alternate Route That You Can Take That Has Stop Signs And Not Red Lights ?
    (" . . . the car/steering wheel shake badly when the car stops at the red light.")


    CSA
  • edited February 2011
    The car would not shake during normal idle when the car is in neutral or park with one bad mount. But, the engine would visibly move when revved in neutral. You can have someone rev the engine while you are looking at the engine. See if it doesn't move a few inches or more while the engine is revved, in neutral, drive and reverse.

    It's true there are more than a few reason why your car will shake in drive at a red light but will be smooth in idle. But you didn't mention very low idle or stalling while in drive at red lights. Does the car also stall at red lights in drive? Is the idle very low?
    There aren't hundreds of reasons why your car will shake violently in drive when stopped but will not shake at all in neutral. There are very few reasons that will not effect idle and will not cause the car to stall in drive while stopped.

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