P050D
Cold Start Rough Idle
The ECU detects rough idle behaviour during the cold-start phase only. Once the engine has warmed up the issue disappears. Typically caused by injector deposits, low compression on one cylinder when cold, or sticky valve guides.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Injector tip coked - poor cold spray patternCommon
- Valve guide sticky when coldPossible
Parts involved
- Fuel Injectors
- Cylinder Compression
- Valve Guides
P050D is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.