Sounds like you ave a misfire. Could be as simple as needing a tune-up.
There are a few reasons why a car shakes when idling at a red light. Some reasons could be the ignition coil, motor mounts, or spark plug problems.
The car needs a tune-up, or the motor mount(s) are bad.
You have a tire out of balance. Have all 4 tires balanced and rotated. If it still shakes have the motor mounts inspected.
water in the fuel can cause an idling motor to sputter and/or die.
Rough idling is whenever the vehicle's motor "misses" or does not fire causing an imbalance and a loss of rotation reducing the motor's power and causing excessive shaking.
Could be in need of a basic tune up.
There could be several reasons why your car is idling hard when the air is on. There could be something restricting air flow to the motor. A mechanic could diagnosis the problem for you.
A car can shake because of a problem in the transmission although this usually is not the problem. I will assume it shakes while it is idling or just starting out. It can also shake due to broken motor or transmission mount(s), bad u joints, a loose harmonic balancer, an unbalanced driveshaft or problems in the rear differential.
check the engine mounts
I would like to change the blower motor in my 1994 Ford Tempo by myself. Do you have any instructions for me to follow?
No
Motor is idling rough.