Car symptoms: what could be wrong
Updated:
When a car won't start, the most common cause is a flat battery, especially in cold weather. If turning the key only gives a click and the lights dim, charge or replace the battery. If the engine cranks but won't fire, the fault is probably in the fuel or ignition system and the fault codes need reading.
Car won't start
Likely causes
- 1Flat or old battery (most common, especially in the cold)
- 2Loose or corroded battery terminals
- 3Worn starter motor
- 4Fuel pump not working
- 5Faulty crankshaft sensor
- 6Immobiliser doesn't recognise the key
What you can check
Notice what happens when you turn the key. If the lights dim and you hear a click, it's probably the battery. If the engine cranks but won't fire, it's fuel or ignition. If nothing happens, check the battery terminals and that the gear selector is in P or N.
Related fault codes
Car won't start, just clicks
Likely causes
- 1Flat battery
- 2Loose or corroded battery terminal
- 3Worn starter relay or starter motor
- 4Bad earth strap
What you can check
Turn the headlights on and try to start. If they almost go out, the battery is flat. If they stay bright, the starter is the more likely culprit. Clean and tighten the battery terminals.
Related fault codes
Car shaking or jerking
Likely causes
- 1Misfire: old spark plugs or a failed ignition coil
- 2Air leak in the intake
- 3Dirty mass air flow sensor
- 4Clogged injector
- 5Worn engine mounts (shakes at idle)
What you can check
If the check engine light is flashing, slow down and stop as soon as you safely can. If it only shakes at a certain speed, the cause may be wheel balancing.
Related fault codes
Loss of power or limp mode
Likely causes
- 1Leaking turbo hose or sticking turbo actuator
- 2Blocked particulate filter
- 3EGR valve clogged with soot
- 4Clogged fuel filter
What you can check
Switch the ignition off for a few minutes and restart. If the power comes back and drops again, have the codes read. Check the turbo hoses for oily residue.
Related fault codes
Rough idle or engine stalling
Likely causes
- 1Dirty throttle body
- 2Air leak
- 3Idle control valve
- 4EGR valve stuck open
What you can check
Listen at idle for a hissing sound. A dirty throttle body is a very common cause.
Related fault codes
Engine overheating
Likely causes
- 1Coolant low or leaking
- 2Radiator fan not running
- 3Water pump failed
- 4Thermostat stuck closed
- 5Head gasket failed
What you can check
Stop and switch the engine off. Don't open the hot expansion tank cap. Check the coolant only once the engine has cooled down.
Related fault codes
Smoke from the exhaust
Likely causes
- 1Black smoke: mixture too rich or a leaking injector
- 2Blue smoke: engine burning oil (turbo, piston rings)
- 3Thick white smoke: coolant burning (head gasket)
What you can check
Note the colour of the smoke and whether it appears when cold or warm. Thin white vapour in cold weather is normal.
Related fault codes
Smell of fuel
Likely causes
- 1Fuel cap loose
- 2Leaking fuel hose or connection
- 3Leaking injector
- 4Leak in the fuel vapour (EVAP) system
What you can check
If the smell is strong or you see a leak, don't drive; it's a fire risk. Make sure the fuel cap is tightened until it clicks.
Related fault codes
Harsh shifts or slipping gearbox
Likely causes
- 1Gearbox oil low or old
- 2Shift solenoid
- 3Speed sensor
- 4Internal gearbox wear
What you can check
Check for oil spots under the car. Avoid hard acceleration and don't drive far in limp mode.
Related fault codes
Want a definite answer?
Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.
Frequently asked questions
What should I do if my car won't start?
Check whether the lights come on and whether the engine cranks. A click with dimming lights points to a flat battery. If it cranks but won't start, have the fault codes read.
Why does my car click but not start?
Usually the battery is flat or a terminal is loose. If the lights stay bright when you try to start, the starter motor or its relay is more likely.
Why won't my car start in the cold?
In the cold the battery delivers less current and the oil is thicker. An old battery then can't cope. On diesels the glow plugs can also be to blame.
Can a symptom tell you exactly what's wrong?
No. A symptom points in a direction, but the fault codes and live sensor data give the definite answer. We read them during diagnostics.