P050D

What it means

P050D is the generic code for a rough idle detected during a cold start. The engine control unit monitors crankshaft speed variation, and in some cases fuelling and ignition feedback, during the warm-up idle period. If the idle is unstable or misfires beyond the allowed limit while the engine is cold, it sets the code. The exact monitoring strategy and causes vary by manufacturer, model and engine.

Symptoms

• Lumpy or shaky idle just after a cold start
• Engine speed hunting or surging during warm-up
• Misfire felt or heard soon after starting
• Engine management light on
• Hesitation or poor pickup before the engine warms up
• Occasional stalling or near-stalling on a cold start

Possible causes

• Worn, fouled or incorrectly gapped spark plugs, or a weak ignition coillikely
• Vacuum or intake air leak (split hose, leaking intake gasket, PCV or breather fault) upsetting the mixture when coldlikely
• Faulty or dirty fuel injector causing poor spray or uneven fuelling on a cold enginelikely
• Faulty coolant temperature sensor or intake air temperature sensor giving wrong cold-start fuellingpossible
• Carbon build-up on intake valves or a dirty or sticking throttle body (depends heavily on engine type, especially direct injection)possible
• Low fuel pressure from a weak pump or restricted filter, or poor fuel qualitypossible
• Low compression or a valve timing fault, or an outdated control unit calibration where the manufacturer has issued an update for this issuerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting coolant temperature, engine speed and load when the code set, and check for misfire codes (P0300 to P0312) or fuel trim codes alongside it.
2. Ask when the fault occurs (only on cold mornings, after short trips, in damp weather) and check for relevant technical service bulletins for that model and engine.
3. Visually inspect the intake pipework, vacuum hoses, breather hoses and connectors for splits, loose clips and damage.
4. Check spark plug condition and age against the service schedule, and test or swap-test the ignition coils if a misfire is indicated.
5. Compare live coolant temperature and intake air temperature readings with actual temperatures on a cold engine to confirm the sensors are plausible.
6. Review short and long term fuel trims at idle, cold and warm, to separate air leaks from fuelling faults.
7. Check fuel pressure against the manufacturer's specification and test injector operation, using the procedure for that engine.
8. Smoke test the intake system for leaks and, if the fault persists, carry out a compression or cylinder balance test.

How to fix

• Replace worn spark plugs and any weak ignition coils with the correct specification parts.
• Repair or replace leaking vacuum hoses, intake gaskets or breather components.
• Clean or replace faulty fuel injectors, and replace a clogged fuel filter where one is fitted.
• Replace any coolant or intake air temperature sensor that reads incorrectly.
• Clean the throttle body and, where the engine type requires it, remove carbon from the intake valves using the manufacturer's recommended method.
• Apply a control unit software update only if the manufacturer lists it as a fix for this fault, and repair any mechanical problems found.

Can I keep driving?

Nearby codes

• P050CGenericCold Start Engine Coolant Temperature Performance
• P050EGenericCold Start Engine Exhaust Temperature Too Low