* Faulty IAC Motor (again): While less likely with such low mileage, it's possible you received a defective replacement the first time, or the new one has failed prematurely. Cheap aftermarket parts are notorious for this.
* Dirty Throttle Body: Accumulated gunk and carbon buildup in the throttle body can interfere with the IAC motor's operation, even if the motor itself is working correctly. Cleaning the throttle body thoroughly is a crucial step in diagnosing idle problems.
* Vacuum Leaks: Small cracks or holes in vacuum hoses can disrupt the engine's air/fuel mixture, leading to erratic idling. Inspect all vacuum lines carefully for damage.
* Mass Airflow Sensor (MAF) Issues: The MAF sensor measures the amount of air entering the engine. A dirty or malfunctioning MAF sensor will send incorrect information to the computer, causing poor idle. Cleaning or replacement might be necessary.
* PCV Valve: A clogged Positive Crankcase Ventilation (PCV) valve can cause a buildup of pressure in the crankcase, affecting the engine's breathing and leading to idle problems.
* Faulty TPS (Throttle Position Sensor): This sensor tells the computer the throttle's position. A failing TPS can send incorrect signals, resulting in a rough idle.
* Engine Coolant Temperature Sensor: An inaccurate reading from the coolant temperature sensor can cause the computer to adjust the air/fuel mixture incorrectly, leading to erratic idle.
* Spark Plugs and Wires: Worn-out spark plugs or faulty ignition wires can contribute to a rough running engine and erratic idle, especially if they're due for replacement at 82,000 miles.
Troubleshooting Steps:
1. Clean the Throttle Body: This is the easiest and often most effective first step. Use a throttle body cleaner specifically designed for this purpose.
2. Inspect Vacuum Lines: Carefully check all vacuum lines for cracks, leaks, or loose connections.
3. Check the MAF Sensor: Clean it with MAF sensor cleaner (following the instructions carefully), or consider replacing it if cleaning doesn't help.
4. Inspect/Replace Spark Plugs and Wires: If these haven't been changed recently, this is a good preventative maintenance item.
5. Test the PCV Valve: You can often check for proper operation by removing and inspecting it for clogs. Replacement is usually inexpensive.
6. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to retrieve any diagnostic trouble codes stored in the vehicle's computer. These codes can provide valuable clues to the problem's source.
7. Consider a Professional Diagnosis: If you've tried the above steps and the problem persists, it's best to take your vehicle to a qualified mechanic for a proper diagnosis. They have specialized tools and expertise to pinpoint the issue.
Replacing the IAC motor again *without* addressing other potential problems is likely to yield temporary results at best. Systematic troubleshooting is key to finding the root cause.
