very rough idle after starting in beolw freezing temperature
Ask shop to check for current and pending drivetrain module diagnostic codes. Is check engine light on?
There are Many possibilities for that symptom, but rough idle when cold could be the fuel/air mixture is too lean, so ask shop to check vacuum leak, maybe do a fuel-trim test. Other possibilities to consider
- Idle air control
- Spark plugs
- Coils
- Fuel injection system
- Engine air filter
- EGR
- PCV