Is a diesel misfire serious?

A single-cylinder misfire will not cause immediate damage but should be diagnosed promptly. Prolonged misfiring can damage the catalytic converter, DPF, and turbocharger.

Can bad fuel cause a diesel misfire?

Yes. Contaminated fuel (water, dirt, or wrong fuel type) is a common cause. If the problem started after refuelling, drain the tank and replace the fuel filter.

How do I know which cylinder is misfiring?

Use an OBD scanner. Codes P0301-P0304 identify the specific cylinder. A cylinder balance test using diagnostic software provides more detail.

Diesel Engine Misfire Causes: Injector Faults & Diagnosis Guide

Updated for 2026 diagnostics & repair guidance

Severity: Urgent

A diesel engine misfire is one of the most common complaints brought to UK garages. While the symptoms are straightforward — rough running, vibration, and reduced power — the causes can range from simple fuel quality issues to serious mechanical faults. This guide helps you systematically diagnose and resolve diesel misfires.

OEM tested & calibrated12-month warrantyFree UK deliveryNo coding required (most models)

Symptoms

Injector failure (most common cause)

Common

Worn, leaking, or sticking injectors are the number one cause of diesel misfires. A leak-off test and injector balance check can confirm this diagnosis.

Glow plug failure

Common

Faulty glow plugs cause misfires primarily on cold starts. The engine runs rough for 30-60 seconds then smooths out as it warms.

Low compression

Serious

Worn piston rings, valve seats, or head gasket failure reduce compression in one or more cylinders. A compression test can identify this.

Fuel system pressure issues

Moderate

A failing high-pressure fuel pump, blocked fuel filter, or air leak in the fuel supply can cause misfires across all cylinders.

EGR valve malfunction

Moderate

A stuck-open EGR valve allows too much exhaust gas into the intake, diluting the air-fuel mixture and causing misfires at idle.

Turbo boost leak

Moderate

A split intercooler hose or failed turbo actuator reduces boost pressure, causing misfires under load.

Most Likely Causes

Injector-Related Causes

Faulty fuel injectors

Worn, leaking, or sticking injectors are the number one cause of diesel misfires. A failed solenoid or eroded nozzle directly prevents proper fuel delivery.

Injector wiring or connector fault

Corroded connectors or damaged wiring to the injector can cause intermittent misfires that come and go.

Other Possible Causes

Failed glow plugs

Faulty glow plugs cause misfires on cold starts that clear after warming up.

Low compression

Worn piston rings, valve seats, or head gasket failure reduce cylinder compression.

Fuel system pressure loss

A failing high-pressure pump, blocked filter, or air leak starves the injectors of fuel.

EGR valve malfunction

A stuck-open EGR valve dilutes the intake charge, causing misfires at idle and low load.

When to Stop Driving

Stop driving if the misfire is accompanied by a flashing engine management light, loss of power with smoke, or if the engine is running on fewer than all cylinders. Continued driving can damage the DPF and catalytic converter.

Quick Diagnostic Steps

1Start with an OBD scan — misfire codes (P0300-P0304) point to the affected cylinder
2Perform a glow plug resistance test (should be 0.5-2 ohms)
3Carry out an injector leak-off test to measure return fuel volumes
4Check fuel filter condition and change if overdue
5Inspect turbo hoses for cracks, splits, or loose clips
6Perform a compression test if other causes are ruled out

Leak-off test guide Injector coding guide

Repair Cost Expectations (UK)

per Injector

£100 - £200

full Set

£600 - £1,200

labour

£100 - £250

Likely Injector-Related?

If your symptoms match the injector-related causes above, replacement is often the most cost-effective solution. Our remanufactured injectors are tested to OEM specifications and come with a 12-month warranty.

View Compatible Injectors Search by Engine Code

OEM tested & calibrated12-month warrantyFree UK deliveryNo coding required (most models)

Need it fast? Same-day dispatch on in-stock injectors.

Order before 2pm for next working day delivery (UK mainland). Not sure which injector? Call us on 020 3355 6581.

Compatible Remanufactured Injectors

OEM bench-tested injectors for engines affected — verified pricing, 12-month warranty, free UK delivery.

Delphi 28342997 OM651 remanufactured diesel injector with RemanufacturedInjector branded box

Delphi A6510704987

Remanufactured Delphi 28272472DNR diesel injector for Mercedes-Benz 2.1 CDI OM651 engines. Direct-fit replacement for C-Class, E-Class, CLA, GLA, GLK, Vito, V-Class, Sprinter and SLK applications. Cross-references A6510704987, A6510702387, HRD351, 28272472. OEM-tested and calibrated with full flow and leak-back verification. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.

£120.00 inc VATIn stock

Fits: OM651, OM651.911, OM651.924, OM651.925

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Bosch 0445110613

BMW 2.0d B47 Remanufactured Common Rail Injector

£120.00 inc VATIn stock

Fits: B47, B47C20A, B47D20, B47D20A

View injector

Bosch 13538514148

2.0L Diesel Remanufactured Solenoid Injector (BMW B47)

£210.00 inc VATIn stock

Fits: B47, B47C20A, B47D20, B47D20A

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Delphi 28307309

Delphi remanufactured diesel injector for Mercedes OM651 applications. OEM tested and calibrated on CR318 PRO test bench. 12-month warranty included. Free UK delivery. Suitable for professional garage use. Exchange unit — return your old injector within 30 days.

£100.00 inc VATIn stock

Fits: OM651.955, OM651.956, OM651.957, OM651.958

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Delphi 28388960

Remanufactured Delphi 28388960 diesel injector for Ford 2.0 TDCi and Peugeot/Citroen 2.0 HDi/BlueHDi DW10 engines. Direct replacement for Ford Mondeo, Kuga, S-Max, Galaxy, Focus, C-Max, Edge and Peugeot 308, 508, 3008, 5008, Expert, Citroen C4, C5, DS4, DS5, Jumpy, Jumper applications. Cross-references 28602948, 9674984080, DS7Q9F593BA, HRD360. OEM-tested and calibrated with full flow and leak-back verification. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.

£120.00 inc VATIn stock

Fits: DW10C, DW10CB, DW10CT, DW10CTED4

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