Q: My car is having a high idle - I replaced the coolant temperature sensor and now the fans don't work

asked by on

When I turn my car on the idle slowly climbs to about 3000 RPM and when I put it in drive it drops to about 1500 RPM

My car has 114000 miles.
My car has an automatic transmission.

This may be related to a dirty or faulty idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage.

When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. This is all done by the idle air control valve. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve. In cases where this valve is dirty or failing, your vehicle may stall instead of slowing to an idle after the release of the throttle. You may also want to check the cooling fan relay switch. As you may know, this is the switch that controls the operation of the fans based upon input data from the coolant fan temperature sensor which you have just replaced. When this relay is not working properly, this may cause the fans to work intermittently or in some cases not at all. I would recommend having an expert from YourMechanic come to your location to diagnose and repair your idle air control valve.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. My car is having a high idle - I replaced the coolant temperature sensor and now the fans don't work

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: what is causing really rough idle.

Rough idling engines can typically be caused by ignition system or fuel system failures. This can be things like spark plugs, spark plug wires, distributor cap, distributor rotor, the distributor itself, fuel injectors, fuel filter, fuel pump, etc. I would...

Q: Is there anyway to bypass the ac compressor they make bypass pulleys but can't find any for an 88 Grand Prix

As long as the a/c clutch bearing is not seized, it doesn't matter if the a/c compressor is locked up. As long as you do not turn the a/c on, this causing the clutch to engage and attempt to run...

Q: Car starts but idles rough and stalls

Hi There, A few different things will usually cause the vehicle to start and then die. A bad ignition coil can cause this if it is beginning to fail, resulting in intermittent starting problems. A dirty or faulty mass air...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...