Engine revs at 4,000 RPM

CRAIGIE005

MEMBER
2006 HOLDEN VIVA
1.8L
4 CYL
2WD
MANUAL
140,000 MILES

When the car starts it runs great, but it idles at 2,500 rpm and then after a few minutes it goes up to 4,000 rpm and stays constant. Throttle cable is not stuck and moves freely. I have replaced the air intake pipe which was split and also the rubber collar on the throttle body. I have checked all hoses and have not found any air leaks. All hoses are connected and all wiring to injectors and sensors seem intact. I cannot get the car to idle, it was okay one day and then the next day this started.
My son drove the car and it was fine and he said he parked the car and hit the concrete bumper stop a little hard. The car has been like it since then. I can only think that the next step is maybe dislodged oxygen sensor. Would that sensor cause this? I am clutching at straws now. Can anyone offer a suggestion?

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,269 POSTS

Hi and thanks for using 2CarPros.com.

Before I begin, please understand that this vehicle is not offered in the US. As a result, none of my manuals provide details specific to it. However, I feel I can still help.

Often times, the evaporative emissions charcoal canister is located in the lower portion of a front fender. Check to see if you can locate it. Once you do, confirm there are no disconnected vacuum lines or damage to the component.

Next, the idle speed on newer cars is controlled by a component called an idle air control valve. This component is located on the throttle body. There is a small valve that moves slightly to allow more or less air enter the engine. If that has failed, it will cause an idle issue as well.

Last, I would like you to check for vacuum leaks. Here is a link that shows how it is done using a vacuum gauge. This will help you determine if there is a leak anywhere.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Here is a link that discusses different causes of high idle. Hopefully, it will help you narrow things down.

https://www.2carpros.com/articles/engine-idles-too-high

Also, here is a link that shows in general how to replace and idle air control valve. I am including it because it may help you locate the one on your car.

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

I hope something here is helpful. Let me know if you have other questions or need additional information.

Take care,
Joe