The most probable reason for the engine to shake at idle is the motor mounts may need replaced. This is generally from the front and rear motor mounts; however, the sides may need replaced as well.
Probably a misfire, it could be in need of a tune up.
Possible cylinder misfire and/or failing engine mounts.
It could be (a) misfiring cylinder(s). Check the condition of your plugs and wires. Also, check if your engine mounts are not worn.
If it is running fine at high revs the most likely problem is an injector
The cause of your 97 Galant idling fast and then slow is a high idle system, either electrical or mechanical. Basically works like this: when the car is cold, usually in the morning, the system will cause the idle to be higher than normal to help heat the engine to normal operating temperature. Once that temperature is reached it will then kick down to a slower idle. Both idle speeds are preset by the factory. This is common on all vehicles, not just the Galant.
bISS iDLE SCREW ON THE THROTTLE BODY
Without much to go on, I would suggest you look for a vacuum leak, especially if the engine runs good under acceleration and only shakes and shudders at idle.
the car is garbage the car is garbage
Idle is computer controlled and is not adjustable.
Idle speed is not adjustable. It is controlled by the engine copmuter. If your idle speed is too high or low you have a problem with a sensor or the idle air controll actuator. Also, a weak battery can cause the idle too be erratic
Do u mean that the car shakes as you are driving, or just that the engine shakes when it is at idle ? Could use more info.
A 1998 Honda Civic shakes when it idles usually due to worn engine mounts. Open the hood and check the engine mounts. See if they are either cracked or brittle. Since the mounts can not absorb the vibrations it will be felt in the cabin.