Acceleration and shaking

I have a 94 grand am V6 and lately the acceleration has gone way down. I was hoping that someone could shine some light on why. I think that it is the spark plugs but I am not sure. Also my car was shaking very rapidly and now it is only shaking a little bit but it seems that the shaking has worsened. At 50 mph is when the shaking starts and when i let off of the gas it will stop. Also my vehicles top speed has gone down from 110 mph to 85 mph. I was hoping that someone could help me out and shine some light on my problems. thank you.

ya know if vibration occurs when traveling especially at higher speeds 50+ id have to say it was something either in the suspension or movement related......ball joints, steering tie rod ends, axels....etc. i would think that if the plugs were causing a miss you would feel it at idle. id suggest getting under the car and looking for something that seems out of place or damaged/broken. can you tell if its from the front or back? left or right side? could be a tire... just a matter of weeding things out.

ya know if vibration occurs when traveling especially at higher speeds 50+ id have to say it was something either in the suspension or movement related......ball joints, steering tie rod ends, axels....etc. i would think that if the plugs were causing a miss you would feel it at idle. id suggest getting under the car and looking for something that seems out of place or damaged/broken. can you tell if its from the front or back? left or right side? could be a tire... just a matter of weeding things out.

It is definetly in the back. it seems to be centered. I dont think that it is a tire because i recently put new front tires on it. I also do feel a miss when I am at idle so it could be the spark plugs so i will try that and i will also look into those other things.

Do you think that it could be a motor mount? please get back with me on this and thank you for your suggestions.

could be a motor mount, but i would think that would be visually obvious. as far as the plugs, i dont think there would be a upper rpm range that it would affect. it would probably be present through the rpm's.

Could be dirt in the wheels

When i am in park and put the car in drive I hold the brake and hit the gas and you can look at the engine and see the whole engine lift up. suggestions?

When the car is in gear it will lift the engine when giving gas and applying the brake , it supposed to do that , its the engines mounts that allow some movement of the engine. But dont do that , you have a fwd only one of those pedals are meant to be pressed at a time and could damage your transaxle.

have you had your rear tires balanced? the weights sometimes fall off. just something to think about.

have you had your rear tires balanced? the weights sometimes fall off. just something to think about.

yes tires were balanced do you think i might need a front end alignment

well if you can feel it at idle then its not a suspension problem.. as soon as mine hit 4th gear at 50mph and trying to hold steady it would shake like all hell.. i found a stripped out spark plug in the back.. you might want to make sure all of your connections are tight and trouble free.

well if you can feel it at idle then its not a suspension problem.. as soon as mine hit 4th gear at 50mph and trying to hold steady it would shake like all hell.. i found a stripped out spark plug in the back.. you might want to make sure all of your connections are tight and trouble free.


I just changed the spark plugs and wires so I do not think that is the problem but thank you

Could be toe or camber/castor if theres nothin else wrong with it.