You can drive, but do not put it off
It jerks under acceleration
At steady throttle everything is fine, but under acceleration the car jerks or hesitates, as if the pedal was released for a moment.
You can usually get home or to a garage, but every day of delay adds to the bill.
What to look at in the live data
- Misfires specifically under load: at idle there may be none at all.
- Fuel trims as the throttle opens — a sharp swing negative points to a delivery shortfall.
- Air flow on a hard press: a dip in the numbers repeats the dip you feel.
- Ignition timing — the unit pulls it back when it hears knock.
Common causes, cheapest first
- Spark plugs at the end of their life: enough spark at idle, not enough under load.
- Bad fuel from the last fill-up.
- A clogged fuel filter or a weak pump.
- A coil that breaks down only under load.
- Clogged injectors.
Codes that show up with this
P0300Random/multiple cylinder misfire detectedP0171System too lean (bank 1) — air leak or not enough fuelP0087Fuel rail pressure too low
These parameters in the reference
Engine RPMShort term fuel trim B1Mass air flow (MAF)Timing advanceFuel injection timingFuel rail pressureFuel pressureCommanded boost pressureAbsolute load value
Lamps that may be on
Do it step by step
Two counters and one swap answer the question a garage charges money for.How to find which cylinder is misfiring
A symptom is not a diagnosis. The same sign comes from a dozen different causes — the readings are what tell them apart, not the feeling.
How the app helps
CarScan shows exactly these readings live, remembers the highest and the lowest value of the trip, and puts them into a report you can hand to a mechanic.