The dashboard shakes heavily while on drive when AC is on especially when I apply brakes. It started after change of engine mounts.

My car has 119212 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hello. Thank you for writing in. The vehicle’s engine had to be removed, at least partially, to access the engine mounts. Pulling the engine involves removing electrical connections, coolant hoses, and a lot of other components. Unfortunately when repairs are this complex the amount of errors that can be made goes way up. The engine will need to be looked over and the engine mount repair verified. Make sure to check every hose, electrical connection, exhaust, and give everything a quick look. It could be as simple as a sensor not being plugged in. The shaking and vibrating should have improved with the engine mount replacement, not worsened.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Common reasons for this to happen:

Loose connections at the positive and negative battery terminals. Very dirty or clogged air filters can also cause your engine to underperform. Loose timing belts are another likely cause. A mechanic will check these and replace them if they appear loose and worn.

If your engine fails to be adequately fed, it can cause the engine to vibrate as you spend time in the car. The shaking can be present as you press on the gas pedal when you drive at a specific speed. A clogged air filter or bad spark plugs or wires are known to cause this issue to develop.
Worn or dirty spark plugs can cause a petrol car`s engine to misfire in one or more cylinders, which can cause vibrations when the car is idling or at running speeds. The easiest solution is to replace your spark plugs and check the related wiring. Engine vibrations can also be due to the air and fuel systems.
The most common reasons a Ford Escape shakes when braking are bad brake rotors, bad brake pads, or a bad wheel bearing.
The most prevalent cause of vibration is problems with your wheels or tires. The potential problems include improper wheel and tire balance, uneven tire wear, separated tire tread, out of round tires, damaged wheels and even loose lug nuts.
A loose or disconnected air hose or vacuum hose can cause quite a bit of violent shaking and vibration in your car`s engine. To correct the problem, simply look for any loose or disconnected hoses and reattach them and replace them as needed.
To help confirm that the vehicle has an engine speed related vibration, with the vehicle stopped, put it into park or neutral and raise the engine speed to the RPM at which the vibration occurred to see if the vibration can be reproduced. If reproduced, diagnosis should begin with engine speed related components.
A: A four-cylinder engine will typically have a slight vibration when idling. This is inherent in the design and may in fact be normal.
While idle, the engine will complete about 10 revolutions or more per second. Because of its vast speed, the gauge displays the counts as multiples of 1,000. A vehicle that is operating normally should measure at about 1,000.
The most common cause of the shaking most often happens near your tires and rims. The tires and wheels connect your vehicle to the road, and if anything is a bit wonky, will notice. It may be something like a broken transmission or a broken control arm.
An indication that a vehicle is not receiving the right mixture of air and fuel is if the vehicle jerks or surges forward at high speed. Several components of the fuel or air intake system could cause this jerking or surging sensation to happen. Issues within these systems can also cause fuel economy to worsen.
One of the main reasons why your vehicle could be vibrating at idle could be due to worn out spark plugs. When a vehicle`s spark plug is faulty, it can interfere with the air-fuel ratio leading to improperly firing cylinders, resulting in a misfire while idling. Replacing your spark plugs will solve this problem.
Low automatic transmission fluid can cause shaking. If the shaking is accompanied by the check engine light, it`s time to visit a mechanic. Drivers of manual cars might discover their clutch master cylinder is the source of the shaking.
Some simple warning signs that the transmission is having problems: Transmission is slow to respond when shifting. Grinding, shaking, vibrating.
Potential causes of a vehicle shaking at idle include a loose gas cap, loose battery cables, a worn throttle sensor, a damaged engine mount, or bad spark plugs. Perform a general inspection of your engine bay to look for damage. If you can`t repair the problem yourself, take the vehicle to a mechanic.
In some cases, a misfire will cause your engine to run rough enough that you feel a noticeable shake. The check engine light will pop on, and it may even begin to flash.
The output of the sensor is read using a multimeter. First, readings should be taken with no vibration. The vibration level should then be increased at a given frequency until vibration levels reach the top of the measurement range for the sensor under test.
3-cylinder engines have more vibration than 4-cylinder engines of the same or higher displacement. However, this does not make the engine any worse.
All engines create a different vibration. 4 cylinder engines are worse because they don`t have the cylinders offset to help balance themselves out like a V6 or V8 engine do.
Abnormal vibration usually is related to one or more of the following causes: engine rotor imbalance, malfunction of mechanical equipment, and airflow disturbances acting over doors or control surfaces that are misrigged or misfaired or that have excessive wear or free play.
The source of the problem could be from tires that are not balanced or a worn-out spark plug. It could also be loose lug nuts. A car also vibrates for a number of reasons when you accelerate. Typically it`s from a damaged inner CV joint.
Motor mounts keep the engine attached to the car. If the vehicle shakes or the engine shudders a lot when stopped at a stoplight, or when parked with the engine idling, it might indicate the motor mounts or transmission mounts are damaged or broken. To see if this is really the problem, shift the car into neutral.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue