I've just replaced two of my senser's, the throttle senser and the air-intake senser. now my engine is idling very high, how do I lower the Idle?

Engine idle speed is limited by reducing the amount of air entering the engine. When an accelerator pedal is pressed, it pulls a cable which opens a throttle plate which then allows more air to enter causing engine RPMs to increase. At an idle, the throttle plate should be closed as to not increase the RPM. There's also a part called the idle air control (IAC) valve which controls how much air bypasses the closed throttle plate at an idle. Lastly, air could enter the engine via an intake gasket or vacuum hose leak; the same rules apply, the split hose or gasket allows air to enter the engine and RPMs will rise. To summarize, a throttle plate not closing, and IAC valve stuck open, or a split intake gasket or vacuum hose could all cause a higher than normal idle condition. You can read more about how to troubleshoot high idle conditions here: https://www.yourmechanic.com/article/how-to-troubleshoot-a-car-idling-at-a-high-speed-by-tim-charlet

Extracted from Engine-Codes.com

Code P0507

Possible causes

- Dirty throttle body

- Electric throttle control actuator misadjusted or damaged

- Faulty Electric throttle control actuator

- Intake air leak

- Poor electrical connection to the Intake Air Control (IAC) valve


What does this mean?

Tech notes

If there are no intake leaks, clean throttle body, adjust engine idle and erase engine code. If the code comes back you may have to replaced the Electric Throttle Control Actuator (Motor) to repair the problem.



There is a factory service bulletin for the following Chevrolet models:



2006-2008 Chevrolet Trail Blazer

2007-2008 Chevrolet Avalanche

2007-2008 Chevrolet Express

2007-2008 Chevrolet Silverado

2007-2008 Chevrolet Suburban

2007-2008 Chevrolet Tahoe

Chevrolet Factory Service Bulletin OBDII Code P0507


What does this mean?

When is the code detected?

Thi P0507 code sets when the Powertrain Control Module (PCM) detects an engine speed outside of the Idle Air Control (IAC) valve range of control.

Possible symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

- Engine hard to start

- Rough or erratic idle speed

P0507 Chevrolet Description

The Idle Air Control (IAC) valve is a Powertrain Control Module (PCM) controlled stepper motor located on the throttle body. The stepper motor drives a valve pintle which protrudes into a passage that bypasses the throttle plates. The PCM commands the IAC valve pintle to extend to decrease the idle speed. The bypass air flow is reduced and the idle speed decreases as the pintle approaches its seat. The PCM retracts the IAC valve pintle away from its seat to increase the idle speed. The retracting of the IAC valve pintle allows more air to bypass the throttle plates. One of the PCMs uses for the IAC system is to maintain a desired idle speed. This DTC sets when the PCM detects an engine speed outside of the IAC\'s range of control.





Read more: http://engine-codes.com/p0507_chevrolet.html#ixzz3ObdI2chF

The idle speed is not supposed to be adjustable. It is controlled by the computer.
What you may have is a vac leak, or the throttle cable may not be adjusted correctly.
If the throttle plate is completely closed, and there are no vac leaks, the idle air control valve is supposed to control idle speed by regulating how much air enters the intake.

High idle could also be of air going in past the MAF mass air flow, just like a vacume leak. Tap the IAC idle air control valve and see if any changes? I normally like to spray water all around the engine specially the vacume pipes and the intake to find leaks (that was old school) now we have smoke machine which is accurate and detects a very small crack.

High idle is usually caused by a vacume leak. First place to check is the cold air intake manifold. All hoses, throttle body, and sensors. Throttle Position(TPS), Mass Airflow(MAS), Idle Air Control Motor (valve) IAC. Controls Idle speed

A malfunctioning throttle system can cause both a high idle as well as an engine stall.

A dirty air intake or cracked air intake tube is often the culprit.

How to Fix an Engine High Idle in Under 15 Minutes

it's on the throttle body. Here's a Quest with same 3.0L engine. These often need cleaning with carb or throttle body cleaner

Idle Air Control (IAC) Valve When the engine (6007) is running but not at idle, the throttle valve controls the amount of air admitted into the engine. The powertrain control module (PCM) (12A650) increases the fuel injection output in proportion to the increased airflow to achieve the appropriate air/fuel ratio. During idle, the throttle valve is almost fully closed. It is therefore necessary for the idle air control system to supply air for combustion during idle. The idle air control (IAC) valve allows a metered amount of air to enter the intake manifold (9424). The camshaft position (CMP) sensor detects engine speed and sends a signal to the PCM. The PCM sends a duty cycle (On/Off) signal to the IAC valve which allows additional air to enter the intake manifold. Air is added by the IAC valve to maintain the set lowest idle speed at which the engine can operate. The idle speed adjusting screw allows adjustment of the airflow into the intake manifold.


Fast Idle Control (FIC) Solenoid The fast idle control (FIC) solenoid helps maintain a constant idle speed while the air conditioning is operating. When the air conditioning is turned on, the front climate control panel sends out two signals. One signal is sent to the powertrain control module (PCM) (12A650) to engage the A/C compressor (19703). The second signal is a ground signal sent to the FIC solenoid relay, to engage the FIC solenoid. The FIC solenoid supplies additional air to adjust the increased engine load.

The throttle body is located on the driver side of the engine compartment.
If throttle plate has not been clean you might want to get a can of carburetor cleaner, remove the inlet snorkel hose and clean around and behind the throttle plate.
The IAC (idle air control) motor may need to be cleaned. The IAC controls your idle rpm.
Good luck, let me know.
Regards,

The O2 sensor input is ignored by the system computer (ECM) until the engine is hot, around 160 deg F, what u might have may be fixed by the following procedure, one other note your 1st tune is due at 100,000 miles, have you reached that? if so replace plugs and check plug wires for damage. Here are the most common causes of surges, stalls at stops, low erratic idle speed, rough idle and engine hesitation, it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Hi,did you replace the engine computer(ecm)?

Check for a vacuum leak around the intake manifold area.It could also be something to do with any of the sensors mounted on the intake manifold,although they should set a trouble code.Manifold air pressure sensor,throttle position sensor,mass air flow sensor,idle air control sensor,etc.Take some brake cleaner or WD 40 and while engine is idling,spray around the intake manifold.If the engine speed goes up or down in relation to your spraying,that's the area of the vacuum leak.Good luck.