Engine Vibration

I have a 1994 Grand AM..with over 150k miles on it. Lately I have noticed that when I accelerate the car, say from 20 mph to 40 mph. I can feel the car going into a higher gear. The engine vibrates and it seems like the engine is changing modes for a few seconds. After I read a certain speed say 45-50mph the car runs smoothly.

I can only feel these vibrations for a few seconds when going from lower speed to higher speeds. Is this normal for old cars? Does anyone know whats going on? Something that need to be looked at?

I dont know much about cars so any help will be appreciated.

Could be motor mount's or could be a ignition problem. Does the engine operate smoothly? and was this a problem that gradually started?. If it is a motor mount it will get worse and could lead to more severe problem.

Yeah the engine operates smoothly. Like I said the vibration happens for a SECOND when I am accelerating and I can feel it when I hit the accelerator.

I will try being more clear, If you have ever driven a manual car-When you acclerate on the 1st gear the gear has a threshhold speed after which you have to change gears again, in an older manual cars you can feel a slight knocking when the car goes into a higher gear and then the engine runs smoothly again.

Something similar happens in my car It vibrates and then everything becomes smooth again. I have an automatic tramission. Do you think I should take it in to get it checked? Is this gonna cost me a lot? Thanks a lot everyone. The problem started gradually.

So your saying its in between shifts?. If so have you changed the tranny fluid and filter in a while? or checked the level?. A healthy tranny should shift smoothly with a fast crisp shifts. If this isn't the case I would suspect it might just be normal wear and tear over the years.

I have to say from the sounds of it at first it seemed like an ignition issue, but like formula suggested along with your update, i would agree with checking your fluid in the tranny. It wouldn't hurt to have it replaced. If your not inclined to doing an fluid change on your tranny any oil change outfit can do it, and I don't think it will cost you anymore than 45 bucks. Trannies are generally a very neglected part of a car and with 150k miles on her she's probably never been in for one.


Marc

You guys mean the transmission fluid right? I am sorry, I just don't know much about cars. :) Yeah I check the transmission fluid level and it looked fine to me. But maybe it has never been flushed and changed. Thank you guys.

You guys mean the transmission fluid right? I am sorry, I just don't know much about cars. :)

Yes. The transmission fluid is what we are talking about. :) If you could picture for one second what it would be like for your engine to never have had an oil change in 150000 miles, pretty gruesome right, picture what it would be like for your tranny. And some cars go to the grave without ever having it changed. The reason your transmission fluid looks "Ok" is because at the bottom of the transmission's oil pan is a magnetic plate that attracts all the metal shavings and dust that wear off the gears and such during the lifetime of the tranny. Plus, the tranny fluid doesn't get contaminated with carbon and gasoline like an engine does. So even if the tranny fluid is bad it is still hard to notice it especially for a novice. One way to tell is by smelling it. If the transmission has been sliping in between gear changes for a long period of time, the fluid will have a "burnt" smell to it and will usually be slightly darker looking than new transmission fluid.

Go out and buy a small bottle of tranny fluid. Take a piece of white paper towel and place a drop of the new fluid on it. Then put a drop of the old tranny fluid from your car next to it and you might be surprised at the difference between the two.\

Marc