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Jerking under acceleration indicates irregular combustion: one or more cylinders are not receiving the right amount of fuel or are not igniting properly. If the engine light flashes while it happens, reduce speed immediately: the catalytic converter is at risk.

When it appears

• Only under hard acceleration: suspect ignition, turbo or fuel pressure
• At constant speed: often the EGR or a leaking injector
• When cold, then improves: glow plugs, temperature sensors, poor-quality petrol

Most common causes

• Worn spark plugs or coils on petrol engines
• Clogged injector or one out of tolerance
• Clogged fuel filter, pump not keeping up with demand
• EGR stuck open recirculating too much gas
• Intake leaks downstream of the MAF sensor
• Dirty throttle body or a throttle valve that sticks

What to do right away

• If the engine light flashes, ease off and have the car checked
• Have the misfire counters per cylinder read: they show where to intervene
• Check fuel pressure under load, not just at idle

How MasterTuning helps

We do not replace parts by trial and error: we read the real values from the ECU (pressures, flow rates, corrections, temperatures) and identify the component responsible. Then we repair and recalibrate the software where needed. Centres throughout Italy.

Read more: vehicle database · what is ECU remapping · original files archive

Does your car have this symptom? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

The engine light flashes during the jerking: is it serious?

Yes: it indicates misfires sending unburnt fuel into the catalytic converter and damaging it. Reduce speed and have the car checked.

Can the jerking be caused by the fuel?

Yes, a poor-quality fill-up or fuel with water in it can cause it: if the symptom starts right after refuelling, it is an important clue.

How do you find the cylinder responsible?

By reading the misfire counters and with a flow/return test of the injectors.