Q: RPMs rise 1100 to 700; then to 1200; then down

asked by on August 18, 2016

Recently the RPMs have been going from 1100 to 700 at idle; then up to about 1200 and then down again. After that there is a rough idle, usually followed by a loss of power if I am accelerating. My car begins to shake, drive roughly, and feels as if it wants to stall. I have replaced the spark plugs, PCV valve, and the air filter. I am wanting to replaced the IAC valve, but I can not find it. Can you tell me where to locate it and give me any advice on solving my car’s problems. Thank you.

Hi there. This is usually either caused by a bad idle control valve or a vacuum leak. The idle control valve is located near the throttle body. It can also be a dirty throttle body. I usually start by cleaning the throttle body and checking the intake for leaks. The intake manifold gasket is also a common failure. If there is no leak or if the throttle body is not the problem then the idle control valve should be replaced. If you are going to have this fixed, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the rough idling problem and other issues that are occurring.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How do you read the lines on the rearview monitor?
When you put your car in reverse and the rearview camera activates, the monitor will show you a picture of what’s behind you, overlaid with four lines of different colors. Understanding what they mean is critical to using this system...
Car starts in On position
The most likely cause of this issue is a faulty ignition switch or lock cylinder. One of the tumblers may have fallen out of place causing a connection to the starter when there should not be. My best recommendation would...
Car window stuck down half way
Hi. When you push the window switch, power flows to a the corresponding window motor. The motor then raises/lowers the regulator, which is a scissor-type lift that attaches to the window. The power window motors and regulators are known for...
Car shaking more the faster I get
Several ideas come to mind. Tire issues sometimes manifest themselves as speed related issues. Out of balance tires will vibrate the faster you go. Also tires that are separated or have flat spots will do the same. If the condition...
What can it be if its not the throttle body?
The throttle body is a common failure on Chrysler's, but there is another component that is key to the throttle system on your car. The gas pedal assembly has a sensor very similar to the throttle body and is an...
oil pressure on 80 what can be the problem?
The best scenario is if the oil pressure sending unit is simply bad. The sending unit can be tested and/or you can simply tee in a known good gauge to rule the sending unit in or out as the cause....
My brother-in-law is fixing the car. First time yes it's been going on about two weeks finally the check engine light came on yesterday.
If the spark plugs are becoming coated with engine oil and there is excessive oil in the exhaust system, then there could be three symptoms to check. Symptoms PCV Valve could be plugged making the engine over pressurize and forcing...
Had a water pump on 2012 Toyota Camry replaced earlier this month by a your mechanic mechanic, now same issue as before, weep hole
Hi there. I've forwarded your question to our sales and service department, who will be able to look up your service to determine what can be done to resolve this issue. They should be contacting you soon. Thanks
My trunk wont close on my 2004 hyundai accent
Hi My. Trunks are one of the simpler components of a vehicle, but just like any other mechanical part, they can malfunction. Some of the common causes would include a trunk latch that is stuck and will not engage, the...

Related articles

10 Biggest Car-Related Headaches and What to Do About Them
You You don’t want to, but if you're a car owner it's inevitable that at some point you will experience car troubles. It's also fairly certain that the machine you rely on will cause you grief when you least expect...
Symptoms of a Bad or Failing Distributor O Ring
If your car has a distributor, common signs the o-ring must be replaced include oil leaks and engine performance issues.
How Long Does a Throttle Kicker Actuator Last?
What What happens when you turn down things in your vehicle such as the air conditioner? It slows down in a controlled manner. Just like when you decrease your speed it's not a sudden loss of power rather it is...