Black smoke when accelerating: which faults cause it?

The most important among the documented faults: delphi piezo injector failure (220/250 CDI), in the OM651; premature turbocharger failure or breakage, in the 1.6 dCi; DPF clogging on additive-type systems (Eolys/cerine), in the 2.0 HDi; wear and failure of the Bosch piezo injectors, in the OM642; clogged particulate filter and oil dilution, in the 1.8/2.2 DI-D; DPF clogging with additive, especially on the 128-138 hp version, in the 2.2 HDi; seized variable-geometry turbo, in the 1.3 Multijet; injector and high-pressure pump wear from contaminated fuel, in the 1.3 Multijet.

SmokeUrgency: Garage soon

Black smoke when accelerating: causes and the faults that trigger it

Black smoke means the engine is burning more fuel than it can use with the air it receives: the mixture is too rich. The most commonly cited causes are dirty or faulty injectors, a blocked air filter, a faulty air flow meter or lambda sensor and, on diesels, the EGR valve or the particulate filter. If the car is also losing power, it should be taken to a garage as soon as possible.^{[1][2][3][4][5]}

33 documented faults cause it in 26 engines. The most important:

High severity: Delphi piezo injector failure (220/250 CDI) · OM651
High severity: Premature turbocharger failure or breakage · 1.6 dCi
High severity: DPF clogging on additive-type systems (Eolys/cerine) · 2.0 HDi

What it means

On diesels, plenty of black smoke when accelerating means too much fuel relative to air: leaking injectors, insufficient turbo pressure, intake leaks or a seized EGR valve. It should not be visible on cars with a healthy particulate filter.

General explanation from MotorFiable. How it shows up in each engine, with sources, is in the list of faults.

What to do now

Garage soon

Ask for the injectors, turbo and EGR to be checked. With a particulate filter, visible black smoke means the filter may be damaged or removed.

Reviewed on 9 October 202638 sources How we work

Most common causes

From most to least likely according to the sources. Under each cause, the part and the related OBD codes.

1. Dirty or faulty injectors
Common cause
Diariomotor says the most common cause is dirty injectors or poor air filtration, and Autofácil includes worn injectors among the causes of black smoke. The extra fuel that does not get burned comes out as black smoke (RACE). When the fault is large, RACE adds that the car jerks and loses power.^[1][2][6][7]
Faults with with the injectors
2. Dirty or blocked air filter
Common cause
According to RACE, a dirty air filter does not let through the oxygen needed and part of the fuel is not burned. RACE cites it among the symptoms of a dirty filter, along with loss of power and higher consumption. It is a cheap part that, according to RACE, is changed every 15,000 km or once a year.^[1][2][3]
3. Faulty air flow meter (MAF) or lambda sensor
Common cause
RACE points to the lambda sensor, which measures the oxygen in the exhaust gases, as a source of a mixture with excess fuel. The air flow meter measures the air entering the engine and, if it is contaminated or damaged, RACE links it to black smoke, loss of power and higher consumption. Autodoc Club associates code P0172 (mixture too rich) with black smoke and cites among its causes a dirty or faulty air flow meter and a faulty oxygen sensor.^[1][4][8]
Faults with with the engine sensors P0172
4. Dirty or blocked EGR valve
Possible cause
RACE includes excess black smoke among the symptoms of a faulty EGR, along with loss of power, rough running and the fault warning light. Autofácil and Diariomotor also cite it among the causes of persistent black smoke.^[2][5][6]
Faults with with the EGR valve
5. Blocked particulate filter or other emissions system
Possible cause
Diariomotor places emissions systems, such as the particulate filter and the EGR, behind black smoke that persists after checking the injectors and air filter. RACE adds that a blocked particulate filter causes loss of power, jerking and an amber warning light, and that the car can go into limp mode.^[2][9]
Faults with with the particulate filter
6. Turbo not working properly (origin of the power loss)
Uncommon
RACE includes the turbo among the causes of a car losing power, along with the injectors, air filter and air flow meter. The sources consulted do not expressly link it to black smoke; it is mentioned because the loss of power may have a different origin from the one producing the smoke.^[10]
Faults with with the turbo

Depending on what you notice

My car is blowing black smoke and losing power

When black smoke and loss of power coincide, RACE links them to a dirty air filter, a contaminated air flow meter or a faulty EGR valve; with a blocked particulate filter the car also loses power and can go into limp mode. RACE points out that on modern cars loss of power usually comes with a warning light, so it is worth reading the codes with a diagnostic machine.^{[3][4][5][9][10]}

Black smoke only when accelerating

Autofácil admits that, if it only happens briefly when accelerating, it can even be normal; if it is persistent, it points to the EGR, injectors, air filter or intake manifold and the air mass sensor. Diariomotor places it at idle or when accelerating, especially on diesels with a lot of urban use.^[2][6]

Black smoke on a diesel or a petrol car

RACE explains that, on a diesel or petrol engine, dense black smoke is mainly due to the mixture of fuel and air. It adds that black smoke and carbon deposits appear more often on diesels, where combustion is by compression rather than by spark.^[1]

Black smoke with the engine warning light on

With the fault light on, a code reading points towards the cause. Autodoc Club cites black smoke among the symptoms of P0172 (mixture too rich), and RACE includes the fault warning light among the symptoms of a faulty EGR or air flow meter.^[4][5][8]

Black smoke on a car with a particulate filter

RACE warns that the carbon deposits produced by poor combustion can make the particulate filter or the catalytic converter stop working prematurely. Diariomotor sees the particulate filter and the EGR behind black smoke that does not go away after checking the injectors and air filter.^[1][2]

What to check first

Note when and how much smoke comes out: a moment when accelerating hard or continuously. Also note whether there is loss of power, jerking or a warning light on, because that decides the urgency.^[2][6][10]
Check the condition of the air filter: it is a cheap part and RACE cites it among the simplest causes of black smoke and loss of power. It recommends changing it every 15,000 km or once a year.^[3]
To help clear carbon deposits, RACE advises getting out on the open road and driving a few kilometres in a lower gear than usual, so that the engine works at higher revs. It does not replace diagnosis if the smoke persists.^[1]
Ask the garage for a fault code reading: P0172 (mixture too rich) points towards the air flow meter, air filter, injectors, EGR or oxygen sensor.^[8]
If the smoke persists after checking the injectors and air filter, ask for the EGR valve and particulate filter to be checked, which according to Diariomotor are often behind the fault.^[2]

Can I keep driving?

Urgency: Garage soon

If the car runs normally, you can drive carefully to a garage, but it should not be left: RACE recommends taking it as soon as possible and warns that carbon deposits can end up damaging the particulate filter or catalytic converter. With a faulty EGR, RACE accepts driving for a limited time, although it does not advise it; for P0172, Autodoc Club says it is not a serious safety hazard and classes it as moderate urgency. If there is a significant loss of power, a red warning light, overheating or strange noises, RACE says you should not keep driving.^[1][5][8][9]

How much it costs to fix

Indicative prices published by the sources cited; they depend on the car and the garage.

Repair	Price
Air filter (part only; RACE describes it as very cheap; price in Spain)^[3]	€8 – €20
Replacing a set of injectors (RACE range; the latest-generation ones can reach €1,500; it does not say whether labour is included; price in Spain)^[7]	€250 – €650
Cleaning the EGR valve (RACE range, which says it includes labour and varies by model; price in Spain)^[5]	€80 – €150
Replacing the EGR valve (RACE range, which speaks of «€250-600 or more» depending on the model and includes labour; price in Spain)^[5]	€250 – €600

Documented faults that cause it

Specific engine and gearbox faults, from most to least important (severity × frequency). Below each title, how the symptom shows up in that fault.

- High severityFrequency: Very frequentOM651Delphi piezo injector failure (220/250 CDI)Black smoke under acceleration because of incorrect fuel metering.Repair (garage): €3,600–€5,900
Source for the symptom in the OM651^[11]
- High severityFrequency: Common1.6 dCiPremature turbocharger failure or breakageBlack smoke from incorrect combustion when the turbo no longer boosts normally.Repair (garage): €3,000
Source for the symptom in the 1.6 dCi^[12]
- High severityFrequency: Common2.0 HDiDPF clogging on additive-type systems (Eolys/cerine)Black smoke when accelerating while the system tries to regenerate the filter.
Source for the symptom in the 2.0 HDi^[13]
- High severityFrequency: CommonOM642Wear and failure of the Bosch piezo injectorsBlack smoke under acceleration due to incorrect fuel metering.Repair: €4,500–€6,500
Source for the symptom in the OM642^[14]
- High severityFrequency: Common1.8/2.2 DI-DClogged particulate filter and oil dilutionBlack smoke may appear during forced regeneration attempts with a very dirty filter.
Source for the symptom in the 1.8/2.2 DI-D^[15]
- High severityFrequency: Common2.2 HDiDPF clogging with additive, especially on the 128-138 hp versionBlack smoke on acceleration while the system tries to regenerate the filter.
Source for the symptom in the 2.2 HDi^[16]
- High severityFrequency: Occasional1.3 MultijetSeized variable-geometry turboBlack smoke when accelerating, from combustion with too much fuel for the air the turbo supplies.Repair (garage): €450–€700
Source for the symptom in the 1.3 Multijet^[17]
- High severityFrequency: Occasional1.3 MultijetInjector and high-pressure pump wear from contaminated fuelBlack smoke from uneven fuel spray in the affected cylinders.Repair (garage): €600–€1,200
Source for the symptom in the 1.3 Multijet^[17]
- High severityFrequency: Occasional1.7 CRDiInjectors that lose calibration with mileageBlack smoke from the exhaust associated with incorrect combustion from the affected injector.Repair (garage): €80–€350
Source for the symptom in the 1.7 CRDi^[18]
- High severityFrequency: Occasional2.5 dCi YD25Turbocharger failureBlack smoke and slow acceleration.Appears at around 120,000 km
Source for the symptom in the 2.5 dCi YD25^[19]
- High severityFrequency: Occasional2.0 BlueHDiDPF clogging on short journeysBlack smoke when accelerating while the system tries to regenerate the filter.
Source for the symptom in the 2.0 BlueHDi^[13]
- High severityFrequency: Occasional2.2 HDiPiezo injector wear and failureBlack smoke from incomplete combustion.
Source for the symptom in the 2.2 HDi^[16]
- Medium severityFrequency: Common1.5 dCiBlocked EGR valve on the early 1.5 dCiHeavy smoke from the exhaust.
Source for the symptom in the 1.5 dCi^[20]
- Medium severityFrequency: CommonBMW N47Clogged or seized EGR valveBlack smoke under acceleration in the more advanced cases of blockage.Repair (garage): €400–€1,500
Source for the symptom in the BMW N47^[21]
- Medium severityFrequency: Common1.3 MultijetEGR valve blocked by sootBlack smoke when accelerating from incomplete combustion when the valve gets stuck in the wrong position.Repair (garage): €130–€400
Source for the symptom in the 1.3 Multijet^[22]
- Medium severityFrequency: CommonBMW M47Blocked and seized injectorsBlack smoke when accelerating when one or more injectors stop spraying fuel accurately.
Source for the symptom in the BMW M47^[23]
- Medium severityFrequency: Common1.6 and 2.0 MultiJet IIEGR valve blocked by soot in urban useBlack smoke when accelerating from incomplete combustion when the EGR is stuck in the wrong position.Repair (garage): €200–€500
Source for the symptom in the 1.6 and 2.0 MultiJet II^[24]
- Medium severityFrequency: Common1.9 JTD/Multijet and 2.4 JTDEGR valve blocked by carbonBlack smoke when accelerating from incomplete combustion when the valve stays in the wrong position.Repair (garage): €130–€800Appears at around 80,000 km
Source for the symptom in the 1.9 JTD/Multijet and 2.4 JTD^[25]
- Medium severityFrequency: Common1.8 TDCiDelphi injector failure (leaks, cracks or poor spray pattern)An injector that sprays poorly or drips produces black smoke when accelerating.Appears at around 45,000 km
Source for the symptom in the 1.8 TDCi^[26]
- Medium severityFrequency: Common1.8 TDCiClogged or failing EGR valveBlack smoke and jerking when accelerating, a symptom Gebrauchtwagenberater links directly to the EGR valve in the C-Max.Appears at around 35,000 km
Source for the symptom in the 1.8 TDCi^[27]
- Medium severityFrequency: Common2.0 Ingenium diéselEGR fouling and AdBlue system faultsBlack smoke when accelerating when soot fouls the EGR or the injectors.
Source for the symptom in the 2.0 Ingenium diésel^[28]
- Medium severityFrequency: CommonSkyactiv-DCarbon build-up in the intake, EGR and injectorsInjectors that spray badly because of carbon can cause black smoke on acceleration.
Source for the symptom in the Skyactiv-D^[29]
- Medium severityFrequency: Common2.0 dCiEGR valve blockageBlack smoke on acceleration if the EGR sticks in a position that alters the air-fuel mixture.
Source for the symptom in the 2.0 dCi^[30]
- Medium severityFrequency: Common2.0/2.2 D-4DInjector wear and failureAn injector that drips or sprays badly can cause black smoke on acceleration because of excess fuel that is not fully burned.Appears at around 30,000 km
Source for the symptom in the 2.0/2.2 D-4D^[31]
- Medium severityFrequency: Common2.5 TDI R5Leaks and play in the unit injectorsSmoke and poor performance from worn injectors.
Source for the symptom in the 2.5 TDI R5^[32]
- Medium severityFrequency: Common3.0 TDI V6Faulty EGR valve and EGR coolerBlack smoke, jerking, higher consumption and less power, which a German guide associates with EGR valve wear.
Source for the symptom in the 3.0 TDI V6^[33]
- Medium severityFrequency: Occasional1.6 dCiInjector failuresBlack smoke from incorrect combustion when an injector does not meter fuel properly.Repair (garage): €250–€1,700
Source for the symptom in the 1.6 dCi^[34]
- Medium severityFrequency: Occasional1.6 and 2.0 MultiJet IIInjector faults and DPF particulate sensor failureBlack smoke when accelerating when an injector loses precision in atomising the fuel.
Source for the symptom in the 1.6 and 2.0 MultiJet II^[24]
- Medium severityFrequency: Occasional2.3 MultiJetLeaking or underperforming common-rail injectorsA commercial leasing website cites black smoke, high consumption and uneven idle.
Source for the symptom in the 2.3 MultiJet^[35]
- Medium severityFrequency: Occasional1.1 and 1.4 CRDiCarbon build-up on the common-rail injectorsBlack smoke when accelerating if an injector delivers more fuel than it should.
Source for the symptom in the 1.1 and 1.4 CRDi^[36]
- Medium severityFrequency: Occasional1.7 CDTISoot fouling of the injectors and EGR valveBlack smoke when accelerating if the injectors drip or the EGR seizes, a typical symptom of this kind of fouling on a diesel.
Source for the symptom in the 1.7 CDTI^[37]
- Medium severityFrequency: OccasionalVM Motori 2.8 and 3.0 CRDWear of the injectors and the high-pressure pumpBlack smoke on start-up or when accelerating hard if an injector delivers more than it should.Repair (garage): €800–€1,400Appears at around 120,000 km
Source for the symptom in the VM Motori 2.8 and 3.0 CRD^[38]
- Low severityFrequency: OccasionalVM Motori 2.8 and 3.0 CRDEGR valve and intake clogged with sootBlack smoke on start-up or when accelerating with the EGR partially stuck.Repair (garage): €150–€600
Source for the symptom in the VM Motori 2.8 and 3.0 CRD^[38]

Which cars it appears in

These faults affect 26 engines. We have documented 210 models from 32 makes with some of the affected versions: open yours to see all its faults.

Engines

Cars with the affected versions

Alfa Romeo

Audi

BMW

See all BMW models

Chrysler

Hyundai

Infiniti

Iveco

Jaguar

Jeep

Kia

See all Kia models

Lancia

Land Rover

Lexus

Lexus IS IIEngine: 2.0/2.2 D-4DYears: 2005–2010

Mazda

Mercedes-Benz

See all Mercedes-Benz models

MINI

Mitsubishi

Nissan

Opel

See all Opel models

Peugeot

See all Peugeot models

Renault

See all Renault models

Saab

Saab 9-3Engine: 1.9 JTD/Multijet and 2.4 JTDYears: 2005–2012

Suzuki

Toyota

Volkswagen

Volvo

Black smoke: causes in your car

210 cars have several documented faults that cause this symptom. Choose yours to see only those that affect it, by engine and by year.

Alfa Romeo 7

Audi 5

BMW 10

Chrysler 4

Citroën 10

Dodge 1

Dodge Nitro

DS 1

DS DS 7 Crossback

Fiat 15

Ford 11

Honda 1

Honda Civic VII

Hyundai 7

Infiniti 2

Iveco 3

Jaguar 4

Jeep 7

Kia 9

Lancia 4

Land Rover 7

Lexus 1

Lexus IS II

Mazda 7

Mercedes-Benz 21

MINI 3

Mitsubishi 4

Nissan 7

Opel 13

Peugeot 12

Renault 15

Saab 1

Saab 9-3

Suzuki 4

Toyota 8

Volkswagen 3

Volvo 3

Black smoke by brand

Fault codes that may go with it

If you have an OBD reader, the code stored by the control unit helps you work out which system is failing.

Frequently asked questions

Is it normal for a car to blow a little black smoke when accelerating?

Only if it lasts a moment: Autofácil admits that if it happens briefly when accelerating, it can even be normal. If the smoke is excessive or persistent, Diariomotor considers it a clear sign that combustion is not working properly.^[2][6]

Can I keep driving if the car blows black smoke?

If it runs normally, you can drive carefully to a garage, but RACE recommends taking it as soon as possible. You should not carry on if there is a significant loss of power, a red warning light, overheating or strange noises (RACE), and with a faulty EGR you can only drive for a limited time.^[1][5][9]

What is checked first when black smoke appears?

Diariomotor recommends starting with the injectors and the air filtration; if the smoke persists, the fault is usually in the emissions systems, such as the particulate filter or the EGR. The air filter is the cheapest check, between 8 and 20 euros according to RACE (price in Spain).^[2][3]

Can black smoke damage the particulate filter or catalytic converter?

Yes, in the long run. RACE explains that the carbon deposits produced by poor combustion can make the particulate filter (on diesels) or the catalytic converter stop working prematurely, so it advises not letting it go.^[1]

Will a car with black smoke pass the MOT?

The sources consulted do not give the smoke limits for the inspection. RACE does warn that driving with a faulty EGR valve, one of the causes of black smoke, can cause problems passing the ITV (Spain's roadworthiness inspection) because of the increase in emissions.^[5]

How much does it cost to fix a car that blows black smoke?

It depends on the cause. According to RACE, an air filter costs between 8 and 20 euros, cleaning the EGR between 80 and 150, replacing it from about 250 up to 600 euros or more, and replacing injectors between 250 and 650 euros (up to 1,500 on the latest-generation ones). These are prices in Spain. The diagnosis decides which applies.^[3][5][7]

Other symptoms: smoke

All symptoms

Has this happened to you? Tell us which fault it was, at how many kilometres and how much you paid: it helps other owners know what to expect. Report your fault.

Sources

Every fact on this page links to its source. If you find an error, let us know.

¿Sale humo negro del tubo de escape de tu coche? ¡Cuidado! Puede significar una avería graveRACE · Motoring press · published 19 March 2024 · consulted 4 October 2026 · in Spanish
Las averías que revela el humo de tu coche diésel o gasolinaDiariomotor · Motoring press · published 13 September 2023 · consulted 4 October 2026 · in Spanish
¿Cuándo hay que cambiar el filtro del aire?RACE · Motoring press · published 22 February 2023 · consulted 4 October 2026 · in Spanish
¿Qué es el sensor MAF del coche y cómo funciona?RACE · Motoring press · published 17 September 2026 · consulted 4 October 2026 · in Spanish
¿Se puede circular con la válvula EGR averiada?RACE · Motoring press · published 20 July 2026 · consulted 4 October 2026 · in Spanish
Humo del tubo de escape: dime el color y te diré la averíaAutofácil · Motoring press · published 4 July 2016 · consulted 4 October 2026 · in Spanish
Problemas con los inyectores: síntomas y fallosRACE · Motoring press · published 16 November 2022 · consulted 4 October 2026 · in Spanish
Código OBD2 P0172 en Peugeot, Mercedes, VW, Citroen: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
¿Se puede circular con el filtro de partículas averiado?RACE · Motoring press · published 31 July 2026 · consulted 4 October 2026 · in Spanish
Mi coche pierde potencia y se queda sin fuerza en las subidas y al acelerarRACE · Motoring press · published 20 January 2023 · consulted 4 October 2026 · in Spanish
Mercedes OM651 turbodiésel: ficha técnica, problemas y tuningMotordinámico · Motoring press · consulted 26 September 2026 · in Spanish
Fiabilité Nissan Qashqai 2 : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité du 2.0 HDIFiches-Auto · Motoring press · consulted 27 September 2026 · in French
Motor diésel Mercedes V6 OM642Motordinámico · Motoring press · published December 2024 · consulted 26 September 2026 · in Spanish
Mitsubishi ASX – Typische Probleme & KrankheitenGebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
Essai, avis et fiabilité des 2,2 HDI 136 chevauxFiches-Auto · Motoring press · consulted 27 September 2026 · in French
Fiat 1.3 Multijet: problemas, fallos y averías más frecuentesTotalrenting · Other source · consulted 26 September 2026 · in Spanish
Hyundai iX35 1.7 Crdi Problemas | Fallos y averías más frecuentesTotalRenting · Other source · consulted 27 September 2026 · in Spanish
YD25 Engine Guide: Specs, Reliability, Problems & Buying TipsAutopartswd · Technical documentation · consulted 5 October 2026
Vanne EGR : problèmes et pannesFiches-auto.fr · Motoring press · published 24 January 2023 · consulted 26 September 2026 · in French
Motor BMW N47: problemas, modelos y qué revisarCarexam · Motoring press · consulted 26 September 2026 · in Spanish
FIAT 500 1.3 MultiJet II: EGR Valve Problems and How to Fix ThemAutoricambi Tritella · Technical documentation · consulted 26 September 2026
BMW 3er E46: typische Probleme und SchwachstellenGebrauchtwagenberater · Technical documentation · consulted 27 September 2026 · in German
Fiat Doblò: problemas, fallos y averías más frecuentesTotalrenting · Other source · consulted 27 September 2026 · in Spanish
Alfa Romeo 156 : les plus et les moinsFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité et pannes du Ford Focus 2 (1.8 TDCi 115ch)Fiches-auto.fr · Owners' forum · consulted 27 September 2026 · in French
Ford C-Max Mk1: Probleme und SchwachstellenGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
Jaguar XE – Bekannte Probleme, Schwachstellen & RückrufeGebrauchtwagenberater.de · Motoring press · published 5 September 2022 · consulted 27 September 2026 · in German
Fiabilité Mazda 3 (2013-2019)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Nissan Qashqai : pannes et avisFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Toyota Avensis (2003-2009) : fiabilité, pannes et rappelsFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Common VW 2.5 TDI PD Problems & IssuesTorque Cars · Technical documentation · consulted 5 October 2026
Audi A6 C6 (4F): Typische Probleme & SchwachstellenGebrauchtwagenberater.de · Motoring press · published 9 September 2022 · consulted 9 October 2026 · in German
Detecta así la avería en los inyectores y ahorra 1.000 €Autopista · Motoring press · published 21 March 2024 · consulted 27 September 2026 · in Spanish
Problemas Fiat Ducato 2.3 MultiJetTotal Renting (web comercial, sin fuentes citadas) · Other source · consulted 8 October 2026 · in Spanish
Kia Rio IV (seit 2017): Typische Probleme & SchwachstellenGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
Opel Meriva A: ProblemeGebrauchtwagenberater.de · Other source · consulted 27 September 2026 · in German
Problemas Jeep Wrangler 2.8 CRDTotal Renting · Other source · consulted 8 October 2026 · in Spanish