The fault code check would be the first thing I checked. That idle is really low. Plugs and coils would have been my first guess but you've already done that.
Are there any noises or rattles from the engine. Cam advance pulleys rattling, misfiring? Did they do an ECU update with the service?
Check for Vacuum Leaks:Vacuum leaks can cause unstable idle. Inspect hoses and connections for any signs of wear or cracks. Use a can of carburetor cleaner and spray it around the engine while it's running. If the engine idle changes, it indicates a vacuum leak in that area.
Idle Air Control (IAC) Valve:The IAC valve controls idle speed. Over time, it can get clogged with carbon deposits. Cleaning it with throttle body cleaner might help. If cleaning doesn't work, consider replacing it.
coolant temperature sensor influences the fuel mixture. If it's faulty, it might cause poor cold starts.
Mass Airflow Sensor (MAF):A malfunctioning MAF sensor can affect air-fuel mixture. Clean it using MAF sensor cleaner or consider replacing it if cleaning doesn't help.
Fuel System Inspection: Ensure the fuel injectors are clean. Consider using a fuel system cleaner in your next tank of gas. Also, check the fuel pressure; a weak fuel pump can cause cold start issues. BG is the brand I prefer to use.
Thermostat Check:A thermostat that's stuck open can lead to a colder engine, affecting cold starts. Ensure the thermostat is functioning correctly.
