Find what is causing the misfire
An engine that shakes at idle, hesitates on acceleration or misfires under load needs investigation in context. We help owners and garages with petrol and diesel running faults, including problems remaining after earlier repairs.
Start with a free code scan and initial assessment. A misfire code identifies detected behaviour; it does not establish whether an injector, ignition component or mechanical fault is responsible.
When to arrange misfire diagnosis
- A rough cold start that improves as the engine warms.
- Uneven idle, shaking or an intermittent engine warning.
- Hesitation or a misfire during acceleration or under load.
- A continuing fault after spark plugs or coils were replaced on a petrol engine.
- Uneven running after injector work, intake cleaning or a software change.
Testing ignition, fuelling and the engine itself
We compare stored faults, relevant live data and the circumstances in which the misfire appears. Petrol ignition and fuelling both matter; a diesel needs checks appropriate to its fuel delivery and mechanical condition.
Pico oscilloscope measurements can help assess signals and component operation. In-cylinder pressure analysis can help investigate compression, valve events and timing-related running problems. We select tests for the engine and concern rather than apply a fixed checklist.
Where the evidence points towards fuelling, injector fault diagnosis on the vehicle helps establish whether removal and bench testing would be useful.
Already changed parts without fixing it?
Bring the original symptoms, code reports and invoices. Tell us what changed after each repair so the investigation builds on that work and distinguishes a continuing fault from a new problem.
Agree the investigation before repairs
After the free assessment, we explain the next useful tests and discuss chargeable work. Access, fault reproduction and any dismantling affect the investigation. Intermittent faults may need more than one observation period.
See our engine diagnostics approach and workshop testing equipment.