Symptom
Fault only appears from a cold start
The first few minutes are wrong and everything is fine once the car has warmed through. Cold is not simply a smaller version of hot — it is a different operating mode, so the fault may be in something that only runs cold. The engine is running rich on a fixed map before its sensors are hot enough to be trusted, glow plugs and heaters are working, clearances are at their widest, and every seal is at its hardest. Say how many minutes it lasts and whether it depends on overnight temperature; a fault that goes at exactly the same point each time is following a temperature threshold somebody can look up.
Also described as: only when cold, only from cold, fine once warmed up, first few minutes, cold start problem, only on cold mornings, فقط وقتی سرد است, فقط صبحها, در حالت سرد, solo falla en frio, pasa solo en frio, solo cuando esta frio, فقط على البارد, المشكلة وقت البرد, تحصل بأول تشغيل الصبح
Some causes mean you should stop driving
2 of the 88 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
Cold is not simply a smaller version of hot — it is a different operating mode, and that is why this pattern narrows the fault so effectively. The engine runs on a fixed enrichment map before its sensors are hot enough to be trusted; glow plugs and heaters are working; clearances are at their widest; every seal is at its hardest; and the battery is delivering its least.
So a fault that is present only cold may be in something that only runs cold, and the list is short enough to work through: the cold enrichment strategy and the temperature signal it depends on, the glow plug circuit on a diesel, oxygen sensor heaters, secondary air injection, and anything whose fit depends on thermal expansion.
Three self-curing mechanisms explain most cold-only running faults, and Russian workshop references set them out clearly: a spark plug fouled with deposits that burns clean once hot, so the cylinder comes back; ignition secondary tracking to earth through damp insulation, which stops when the moisture evaporates; and a hydraulic lifter that has drained overnight and does not take up its clearance until oil pressure reaches it.
The fourth has no self-cure and is the one to catch: the mixture is simply wrong for a cold engine, because the coolant temperature sensor is reading warmer than reality. It produces no warm symptom at all, which is exactly why it survives for months.
Say how many minutes it lasts and whether it depends on overnight temperature. A fault that goes at exactly the same point each time is following a temperature threshold somebody can look up — and the diagnosis has to be recorded from a genuinely cold start rather than attempted in a warm workshop.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Rough for the first minute on one cylinder, then perfect | A plug fouled with deposits that burns clean once hot, or a lifter that has not pumped up with oil | Record misfire counters from a genuinely cold start — the workshop cannot reproduce this warm. Inspect that cylinder's plug. | Renew the plugs as a set and address why that cylinder fouls; a noisy lifter that quietens with pressure is its own repair. |
| Worse in damp weather, better in a dry spell | Ignition secondary tracking to earth through damp insulation until the moisture evaporates | Inspect leads and boots for tracking marks; look for a visible corona in the dark with the engine running. | Renew leads, boots or cap. Tracking marks do not clean off. |
| Rough cold with no single-cylinder misfire | The mixture is wrong for the temperature — a coolant temperature sensor reading warmer than the engine is | Compare live coolant temperature against ambient after the car has stood overnight; they should agree. 40 °C on a frosty morning is the fault. | Renew the sensor and inspect its connector. This produces no warm symptom, which is why it survives. |
| Diesel, rough or hard to start cold only | Glow plug circuit, or injector delivery out of tolerance when cold | Measure each glow plug's resistance and confirm the relay energises; read injector correction values from a cold start. | Renew glow plugs as a set with the relay; treat an outlier injector separately. |
| Lasts a consistent number of minutes and depends on overnight temperature | A temperature threshold in the strategy — closed loop, heater operation, or enrichment tapering | Log coolant temperature against the moment it clears. A repeatable threshold is a strategy rather than a marginal part. | Diagnose what the threshold governs — commonly a sensor heater or the enrichment map's input. |
| Lean trims cold that normalise once warm | Unmetered air — its effect is largest when airflow is lowest, and hardened rubber leaks worst cold | Smoke-test the induction, and compare trims cold against warm rather than reading them once. | Renew the leaking hose or gasket. Rubber that has hardened is the reason the symptom follows temperature. |
-
Rough for the first minute on one cylinder, then perfect
- Likely cause
- A plug fouled with deposits that burns clean once hot, or a lifter that has not pumped up with oil
- How to confirm it
- Record misfire counters from a genuinely cold start — the workshop cannot reproduce this warm. Inspect that cylinder's plug.
- What fixes it
- Renew the plugs as a set and address why that cylinder fouls; a noisy lifter that quietens with pressure is its own repair.
-
Worse in damp weather, better in a dry spell
- Likely cause
- Ignition secondary tracking to earth through damp insulation until the moisture evaporates
- How to confirm it
- Inspect leads and boots for tracking marks; look for a visible corona in the dark with the engine running.
- What fixes it
- Renew leads, boots or cap. Tracking marks do not clean off.
-
Rough cold with no single-cylinder misfire
- Likely cause
- The mixture is wrong for the temperature — a coolant temperature sensor reading warmer than the engine is
- How to confirm it
- Compare live coolant temperature against ambient after the car has stood overnight; they should agree. 40 °C on a frosty morning is the fault.
- What fixes it
- Renew the sensor and inspect its connector. This produces no warm symptom, which is why it survives.
-
Diesel, rough or hard to start cold only
- Likely cause
- Glow plug circuit, or injector delivery out of tolerance when cold
- How to confirm it
- Measure each glow plug's resistance and confirm the relay energises; read injector correction values from a cold start.
- What fixes it
- Renew glow plugs as a set with the relay; treat an outlier injector separately.
-
Lasts a consistent number of minutes and depends on overnight temperature
- Likely cause
- A temperature threshold in the strategy — closed loop, heater operation, or enrichment tapering
- How to confirm it
- Log coolant temperature against the moment it clears. A repeatable threshold is a strategy rather than a marginal part.
- What fixes it
- Diagnose what the threshold governs — commonly a sensor heater or the enrichment map's input.
-
Lean trims cold that normalise once warm
- Likely cause
- Unmetered air — its effect is largest when airflow is lowest, and hardened rubber leaks worst cold
- How to confirm it
- Smoke-test the induction, and compare trims cold against warm rather than reading them once.
- What fixes it
- Renew the leaking hose or gasket. Rubber that has hardened is the reason the symptom follows temperature.
Codes that produce this symptom (88)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0077 Low Tyre Pressure Typical of this code Moderate
- P000A A Camshaft Position Slow Response Bank 1 Typical of this code Moderate
- P000B B Camshaft Position Slow Response Bank 1 Typical of this code Moderate
- P000D B Camshaft Position Slow Response Bank 2 Typical of this code Moderate
- P00B2 Radiator Coolant Temperature Sensor Circuit Range/Performance Typical of this code Moderate
- P013E O2 Sensor Delayed Response - Rich to Lean Bank 1 Sensor 2 Typical of this code Moderate
- P014A O2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 2 Typical of this code Moderate
- P01CB Cylinder 1 Injection Timing Performance - Over Retarded Typical of this code Moderate
- P01CD Cylinder 2 Injection Timing Performance - Over Retarded Typical of this code Moderate
- P01CF Cylinder 3 Injection Timing Performance - Over Retarded Typical of this code Moderate
- P01D3 Cylinder 5 Injection Timing Performance - Over Retarded Typical of this code Moderate
- P01D5 Cylinder 6 Injection Timing Performance - Over Retarded Typical of this code Moderate
- P020A Cylinder 1 Injection Timing Typical of this code Moderate
- P020C Cylinder 3 Injection Timing Typical of this code Moderate
- P024A Charge Air Cooler Bypass Control A Range/Performance Typical of this code Moderate
- P0380 Glow Plug/Heater Circuit A Typical of this code Moderate
- P0381 Glow Plug/Heater Indicator Control Circuit/Open Typical of this code Low
- P0410 Secondary Air Injection System A Typical of this code Moderate
- P050A Cold Start Idle Control System Performance Typical of this code Moderate
- P050B Cold Start Ignition Timing Performance Typical of this code Moderate
- P052F Glow Plug Control Module 1 System Voltage Typical of this code Moderate
- P0561 System Voltage Unstable Typical of this code Moderate
- P056E Cold Start Turbocharger/Supercharger Boost Control A Performance Typical of this code Moderate
- P058C Battery Monitor Module Temperature Monitoring Performance Typical of this code Moderate
- P05AE Active Grille Air Shutter B Performance/Stuck Off Typical of this code Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others with this symptom
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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