My engine has a high idle why?

You may have an air leak at the throttle body or a problem with the IAC check this first. This guide can help us fix it

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

Please run down this guide and report back.

OK, good place to start looking, good luck with this.

Good morning,

The idle air control motor is supposed to adjust engine RPM according to load. When the motor sticks or does not work correctly, this will result.

You cannot clean this motor as the dirt is in an area you cannot access.

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

It is located behind the throttle body on the neck of the upper intake plenum. It attaches with 2 8mm bolts and an electrical connection.

I attached a picture for you of the location.

Roy

For starters scan the PCM (computer) for codes

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If the PCM sees a problem it will store a code that will help in diagnosing the problem, get back with the exact codes.Sounds like it could be the IAC (idle air control) sticking, but will need to be scanned as to why it wont go over 12 mph.

Hello,

It sounds like you have an IAC motor that needs replacement. Here is a guide that will help you get the job done and some diagrams (Below) to show what is it like on your car.

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

I would double check the large vacuum hose, they like to leak at the rear of the engine.

Does the engine have an EGR valve?

Please let us know what happens.

Cheers, Ken

Good afternoon,

Why do you think it is the coolant sensor? It does not control idle speed.

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

You said you knew where it was but you want to know where it is? Please explain.

The sensor is located just under the intake manifold on the left front of the engine.

Roy

REMOVAL
1. Disconnect the battery ground cable.

2. Remove the bolts and the accelerator control splash shield.

3. Remove the Idle Air Control (IAC) valve electrical connector.

4. Disconnect the throttle bypass hose.

5. Remove the bolts and the IAC valve.

INSTALLATION
1. To install, reverse the removal procedure.

Good morning,

When you had the EGR off, were the passages clear of all carbon? If some carbon is in there and holding the valve open, it creates a vacuum leak and the idle will be high.

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

Also, remove the connector for the idle air control valve and see if the idle drops.

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

I would also clean the throttle body of all carbon as well.

https://www.2carpros.com/articles/throttle-actuator-service

Roy

Give the idle air control valve a tap with a screwdriver handle, these are notorious for sticking, and especially after a decarb service.

Hi,

It sounds like you have already done a lot. Have you checked for engine vacuum leaks? Also, have you checked to confirm fuel pressure is within spec?

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

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know if you found any diagnostic trouble codes also.

Take care,
Joe

Hi,

The engine needs an air source to run faster. Either the throttle is not returning or the engine is getting air from another source.Check the throttle Cable, IAC/Auxiliary Air Valve and Cruise Control engagement, PCV valve hanging open.Check for an overheat situation - PCM commands faster idle for attempted cool down.High idle after driving for a while and slowing for a stop, idle speed increases. After driving for a while and slowing for a stop, idle speed increases. Makes me think the brake booster is faulty and once in a while the seal hangs open and allows atmosphere air into the vacuum side which would raise the engine speed and at the same time make it harder to brake.Put a vacuum gauge on the booster between a check valve and the booster and step on the pedal periodically after running engine to build vacuum before each
attempt.The booster should drop vacuum but still have some left for a second attempt.

if not, and it bleeds down, it's bad. Note: On vehicles that have curb idle speed adjustment capability, An idle speed that is too high will cause vehicle to creep, have harsh engagements and harsh closed-throttle downshifts. On vehicles equipped with an Exhaust Gas Re-circulation (EGR) system, it is important to check the system for proper operation. The Manifold Absolute Pressure sensor, Mass Air Flow sensor, and Coolant Temperature sensor can cause intermittent high idle also. Try unplugging one at a time see if it makes a difference in the RPM's. I'm attaching repair guides below. Let us if you more assistance.

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

Thank you
Joe Terwilliger

We need to start with checking for codes. The fact that you replaced the TPS is good but we could still have a wiring issue or control module issue. Basically if we have codes we can chase that down but if there are no codes then we will need a scan tool to see what the PCM is seeing as the TPS signal voltage. Engine off with a closed throttle, it should be around 1 volt. If the PCM is seeing something different then that points to the issue. At that point, we need to monitor the voltage on the 3 wires are the back of the sensor. You should have ground, 5 volt reference, and then 1 volt on the signal wire with the engine off and throttle closed.

Since the sensor is new, I suspect this is what you have. At that point, if the PCM is showing a different voltage for the TPS then we know either the wire is the issue or the PCM is faulty.

Lastly we need to check for a vacuum leak just to rule that out.

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

Let me know if you have questions and we can go from there. Thanks