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Describe the problem

Plain words are fine — "idles rough and smells of fuel" works. It is matched against the corpus's own symptoms, parts and causes, not guessed at.

Or start from what you can notice

Each phrase is a documented symptom. Pick the closest to see which trouble codes are known to cause it.

Warning lights and messages

Starting and switching off

Battery going flat overnight Clicks but will not crank Engine cranks but does not fire Engine shudders when switched off Engine starts then stalls immediately Engine turns over slowly Engine will not crank in park or neutral Engine will not shut off Engine will not start Hard starting Stop-start system not working Vehicle will not power on

How it drives

Engine cuts out when fuel is low Engine cuts out without warning Engine runs rough at idle Engine stalls Engine stalls when coming to a stop Engine stumbles when changing between petrol and gas Engine will not rev above idle Erratic or surging idle Hesitation or stumble under acceleration Idle stays high when the engine is warm Increased fuel consumption Loss of power Poor performance at high engine speed Power comes back after switching off and restarting Reduced engine power or limp mode Rough running only when cold Rough when in gear at a standstill but smooth in neutral Shudder at steady cruising speed Throttle feels slow or disconnected Vehicle will not switch over to gas Vibration felt through the vehicle

Noises

Booming or droning at low revs in a high gear Droning or humming that rises with road speed Engine pinking or knocking under load Exhaust sounds louder than usual Flutter or chatter from turbocharger on lift-off Hissing or rushing air under acceleration Loud buzzing or whirring after a cold start Loud whine or siren noise from turbocharger Rattle from engine on startup The cabin is suddenly much noisier Ticking or tapping from the top of the engine Unusual engine noise Whine that changes when you turn the steering wheel Whirring or grinding as the engine starts

Smoke, smells and leaks

Black smoke from exhaust Blue smoke from exhaust on startup Burning smell Engine is using oil between services Rotten egg or sulphur smell from the exhaust Smell of fuel Smell of unburnt fuel from exhaust Steam or coolant smell from engine bay Visible coolant leak Visible fuel leak Visible oil leak Water dripping under the car in warm weather White smoke from exhaust on cold start White vapour from the exhaust that clears

Gearbox and drivetrain

Binding or juddering when turning at low speed Clutch pedal feels wrong or bites differently Delay before the car moves when selecting drive Delayed engagement when selecting drive Four-wheel drive will not engage Gear selector position displayed incorrectly Grinding when changing gear Harsh or delayed gear changes Harsh or jerky gear changes Judder when pulling away Manual shift mode not working No reverse gear One gear slips while the others are fine Revs flare between gear changes Stuck between gears Transmission overheating warning Transmission slipping Transmission stuck in one gear Transmission will not change gear Vehicle rolls when parked Vehicle will not move in any gear Vehicle will not shift out of park Whine or hum from the transmission

Brakes, steering and suspension

Brake pedal feels soft or spongy Brake pedal pulses or vibrates Grinding or scraping noise when braking Hard brake pedal Heavy or stiff steering Parking brake will not release Steering feels heavy or inconsistent Steering wheel is not straight when driving straight Suspension feels harsh or uncontrolled Vehicle pulls to one side Vehicle sitting low or unevenly Wheels lock or drag while driving

Heating, cooling and climate

Air conditioning blows warm Air conditioning not engaging Coolant level keeps dropping Cooling fans running constantly or not at all Engine slow to reach operating temperature Poor heater performance Problem only happens with the air conditioning on Temperature gauge moves up and down Temperature gauge reading high Windscreen will not demist

Instruments and electrics

Brake lights not working Brake lights stay on when the pedal is released Central locking not working Dashboard gauges not working Diagnostic tool cannot connect Door mirrors not adjusting or folding Door or boot shows as open when it is shut Electric seat not adjusting Electric window not working Electronics reset or reboot while driving Fuel filler flap will not open Fuel gauge reading incorrectly Headlights not adjusting or aiming correctly Headlights not coming on Incorrect outside temperature display Lights flickering or dimming Speedometer reading incorrectly or not at all Tachometer reading erratically or not at all Trip computer or range display incorrect Warning chimes not sounding

Driver aids and infotainment

Adaptive cruise control unavailable Blind spot monitoring not working Collision warning system unavailable Cruise control will not engage Cruise control will not hold speed Driver assistance features unavailable Emergency call system unavailable Hands-free calling not working Head-up display blank or incorrect Navigation or map display not working Parking sensors beep for no reason Parking sensors not working Radio or infotainment screen not working Reversing camera not displaying Sound from only some of the speakers

Hybrid and electric

Battery charge display swinging rapidly Charging cable or flap will not release Charging stops before the battery is full Hybrid running on engine only Loud fan noise after charging or a hard drive Reduced electric-only range Regenerative braking feels weaker or has gone Vehicle charges more slowly than usual Vehicle will not charge Whine or growl from the electric motor

Emissions and inspection

AdBlue being used faster than usual Emissions test failure Emissions test readiness monitors incomplete Fuel nozzle keeps clicking off when refuelling No noticeable change in how it drives Particulate filter regenerating too often

When it happens

Fault only appears from a cold start Fault only appears in wet weather Fault only appears once the engine is hot Only happens above a certain speed Only happens over bumps or on rough roads Only happens when towing or heavily loaded Only with the headlights or heater on The fault comes and goes

Something changed recently

Fault appeared after recent work on the car Problems started after battery work or a jump start Problems started after driving through water Ran badly after filling up Started after an accessory was fitted Started after the car stood unused

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.