Car shakes, but only when I press the gas above 30-40mph. Need help.?

Question

The car is a 1987 Oldsmobile. The car drives more or less fine at slow speeds below about 40 mph. Somewhere around 30-40, and only when accelerating, the car seems to shake/vibrate. It feels like you're driving on a rough surface even when the road is smooth. If you take your foot off the gas, the shaking stops and it becomes smooth again. It was recently purchased, so I don't think it's something that could have been easily noticed and repaired by the dealership. Thanks in advance for your help, and let me know if more information is needed.

Added detail: It doesn't seem to go away at a higher speed. It seems to be correlated with pressing on the gas pedal somehow.

The shaking goes away almost immediately when you take your foot off the gas pedal.

Thanks to everyone for the help.

Answer 1

does the shaking stop immediately after you take your foot off the accelerator? if it does it wont be your tyres or wheel balance. if you take your foot off and the shaking gradually stops, then yes,tyre problem

Answer 2

FIRST OF BAD WHEEL ALIGHNMENT WILL MAKE THE CAR PULL TO ONE SIDE OR THE OTHER SO IT ISN'T THAT
SECOND IT ISN'T YOUR TYE BAR OR YOUR STEERING RACK (sorry wrong symptoms)
although the gear box is a possibility
the most likely cause is your front wheel balance is in correct
take the car to a tyre shop/garage and have them check your wheel balance ( a fairly good rule of thumb is up to about 50-60 mph the front wheels over 50 rear wheels)
the other possibility is that one or more of the road wheels/tyres are distorted either way this is something that is best check by the professionals

Answer 3

I’m no mechanic, but fix my Junker a lot.
If you car is a manual, you may need to stay in third gear longer before shifting up to fourth. If your car is an automatic transmission, it may need recalibrated which shouldn't cost too much at the shop. Don’t let them sell you a new transmission! Shops are good for that kind of stuff.

There is also a chance that it might be the carburetor. This is easy to check. Drive your car so it shakes for a bit; pull of the road and smell the exhaust. If it smells strongly of gasoline you may have a bad O ring in you carburetor. Drill the shop on your results.

Hope this helps.

Answer 4

Sounds actually just like the allignment is off and it could be something easilly missed in a used car. Most of the time they don't pay much attention to the used cars. Try accelerating up to the speed of 60-70 and see if the problem goes away. If it does it is just an allignment problem most likely and can be fixed almost any local mechanic shop.

Answer 5

They will always tell you it is the most expensive part. I have three mechnics in the family, trust me it can be as simple as the transfer case needing to be replaced or welded. Depending on the car too, if you have a jeep model I would check your turk converter. Don't go stright to the tranny.

Answer 6

First have your tyre pressure checked to ensure that they are thesame-an unequal pressure could be responsible for vibration in a new car.
Secondly check to ensure that the WHEEL BALANCING is okay-it is mainly responsible for most vibration during motion.

Answer 7

Your tire(s) may be damaged or have a knot in one of them. Tires with a knot in them will appear to be normal at first glance but you must look them over good to find it unless it is really bad. It is usually towards the inside of the tire.

Answer 8

hard to answer without actually being there.one of the problems than can occur is that your wheels are out of round. another is that your tires are out of balance

Answer 9

it could be a few things. if your tyrod is not working anymore or your steering rack not working it will do that. same thing happened to me. hopefully though it is just your alignment, or your tires need to be balanced. mainly find a mechanic you trust

Answer 10

try taking car to a tyre fitters (kwik fit,national etc.) it sounds like you need wheels balancing.