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Describe the problem
Lubock analyses the causes and guides you through the checks
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Likely causes
- 1Worn coils or spark plugs
- 2Dirty or faulty injectors
- 3Slipping clutch (manual gearbox)
Checks to perform
- Note at which rpm the jerks appear (idle, pick-up, high speed).
- Check whether the check engine light comes on and read the OBD-II code.
- On petrol, coils and plugs are the first check.
- If revs rise without the car speeding up, think clutch.
Jerks feel like surges and pauses on acceleration. They almost always come from ignition, fuel or transmission. Working out whether they appear at low or high rpm helps narrow the cause.
Worn coils or spark plugs
On petrol it's the most common cause: a faulty coil or plug causes misfire, the car jerks and sometimes shakes at idle. The check engine light often flashes.
Dirty or faulty injectors
Clogged or poorly spraying injectors cause hesitation on acceleration and roughness. A cleaning additive in the tank can help mild cases.
Slipping clutch (manual gearbox)
If revs rise but speed doesn't, the clutch slips: more marked jerks uphill or when picking up. It indicates disc wear, often with a burning smell.
Dirty MAF or throttle body
A dirty throttle body or altered MAF cause hesitation when you press the accelerator, especially when picking up.
Air in the fuel system (diesel)
On diesels, air in the fuel lines causes jerks and hard starting, often after a poorly fitted filter or a tiny leak.
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