Engine shakes on cold start
Engine vibrates the first 30-60 seconds after starting in cold weather — what it means and whether it's dangerous.
Cold-start rough idle is almost normal for GDI engines. But if it persists past warm-up, it's worth investigating.
Main causes: (1) misfires due to over-enrichment on cold start — ECU dumps extra fuel, and if injectors leak the mixture goes too rich; (2) dirty IACV can't hold 800-1000 RPM target; (3) VVT system slow to actuate on cold oil.
OBD-II check: read STFT right after cold start. If STFT is sharply negative (−20% or lower) — ECU is trimming enrichment. Watch RPM: normal cold idle is 1200-1500 RPM tapering down.
First diagnostic steps
- Log RPM and STFT in the first 60 seconds after start
- Inspect spark plugs for oil fouling or black carbon
- Clean throttle body and IACV
- Check fuel rail pressure after pump prime
- Read VVT codes (P0011-P0028)
Likely fault codes
Click a code for detailed description, causes, and diagnostic plan.