Skip the auto shop - Our mechanics make house calls

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.

A: This may be related to a dirty or faulty id...

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?

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!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: 2005 BMW 645Ci only shifts and drives in 1st and 2nd gears

Hello. I would need to check the transmission fluid condition to tell you for sure what is going on. If the fluid is dark or smells burnt then it more than likely needs a transmission. I usually scan the computer...

Q: oil pump drive

Hello there, thank you for asking about your 1993 Pontiac Grand Prix. The pump is self priming. If the red Oil Pressure Warning Light is not on, there is sufficient oil pressure. When engines are assembled, the oiling system is...

Q: Car battery light on... New battery and alternator but keeps dying

Hello. If your charge indicator is on, this indicates a problem in the system. The charge indicator will have a resistor that is about 390 ohms when tested and if it is bad then may cause light to come on....

Related articles

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...
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
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...