Skip the auto shop - Our mechanics make house calls

Q: Engine shakes when heat is on

asked by on

I have a 2001 PT Cruiser. Engine shakes/vibrates loudly for like 2-3 seconds at a time on cold start only when I turn on the heat and let the car idle in park position. Does this for a while until car is "warmed up". Doesn't do it if I leave the heat off while letting it idle in park position on cold start. What can be the cause of this? Thanks.

My car has 106000 miles.
My car has an automatic transmission.

Hi There, This may potentially be a result of the change in heat in the coolant that results when turning on the heater while the car is still warming up. As you may know, when the car is first started when cold, the coolant temperature sensor reads the temperature of the coolant and relays this information to the ECU. Te ECU uses this information to make adjustments to the air/fuel ratio (adding more fuel) to the fuel supply as the engine requires more fuel to run when the engine is cold due to the difference in air density at colder temperatures. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Engine shakes when heat is on

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car doesn't run after Check Engine light came on

Hi there. When the check engine light starts flashing that means that the engine is experiencing a cylinder misfire. If the engine ended up stalling afterwards then you may have a fuel pump that failed or possibly a timing belt...

Q: Having problems with clutch

If the hydraulic clutch master cylinder and slave cylinder are bad then it will not push in the clutch pressure plate far enough to allow it to disengage. If the hydraulic system is pushing the pressure in far enough and...

Q: Are the motor mounts touched during a tune up? When are the motor mounts touched?

There is nothing in a basic tune up that would require loosening or touching the motor mounts. If the motor mounts are in fact loose, they could potentially cause damage to the axles if the motor were to shift enough...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.