Idle rpm dear sir/ why nubira 2 with throttle motor rpm rise and fall at idle. thanks

What Colorado do you have ? 2 wheel or 4 wheel drive ? Sport ,sport LS 3.5L , Z71, Z71 LS. etc. what size engine ? an does it have electronic throttle control ? I have factory service info an it is not showing that code .
DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
DTC P0507

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0507 Idle Speed High
Cleaning the throttle body mite take care of it !
Cleaning Cleaning An Electronic Throttle Body Safely

Hi,

Based on your description, could be anything:

• throttle control (including A/C compensator);
• auto choke;
• engine management;
• auto cruise (if your model has one)

A couple of clarifying questions:

1. What is your standard set idling RPM, 1000? with or without A/C?
2. Automatic or conventional/manual trnasmission?
3. When was the last major tune-up? What parts were replaced?
4. Does it sound like misfiring also?
5. Any other indicators, hard starting, long warmup, stalling, excessive gas consumption, smarting to the eyes exhaust fumes?
6. Does your battery light lits up?

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

the throttle body idle lever can wear out causing cars rpm to drop-chec gauge to confirm-wil be around 500------also motor mounts wear-need to test using emergency brake and watchn engine rise n fall

check the firing order as it indicates 2 wires crossed

Disconnect battery for 5 minutes then try. Memory problems.

Yes. It's called the idle air control motor. IAC

Unstable idling especially rising and falling RPM (Described as Hunting) can often be traced to an air leak in the inlet side of the engine. Unmetered air is being drawn into the engine causing temporary confusion in the management system which adjusts the fuel to compensate... this increases the RPM ... the engine then realizes that the throttle has not been depressed and backs off the fuel delivery. Thus dropping the RPM... this cycle then repeats.

If you can find a cracked, damaged or loose pipe then great!.. If not it may be a leaking gasket.
Which will be harder to locate.

Idle is computer controlled and not adjustable. If there is an idle problem, may be idle control motor (throttle body mounted) or bad throttle position switch.

Check throttle cable for fraying /binding. Check for vacuum leaks, check tps and any idle control motors fro proper operation, check throttle plate for carbon buildup.

The IAC valve requires resetting .
First locate the IAC valve located on the side of the throttle body and has 4 wires going to it .Procedure is as follows
Ignition key on ,unplug the IAC ,turn key off ,reconnect the IAC .do this 3-4 times .restart the car and hold the rpm at 2000 rpm and slowly lower until it idles by it self .