Smart ForFour 454
Weaknesses, engine ratings and buying advice
177 PS
ForFour · Benzin
Pocket rocket with four seats
Legendary!95 PS
1.3L Benzin
4 weaknesses
Good Choice109–177 PS
1.5L Benzin
4 weaknesses
Stay Away!Generations
Engine Overview
The Smart ForFour 454 is available with 4 engine variants — from 64 to 177 hp.
Mitsubishi-based 3-cylinder diesel for the ForFour 454. Same platform as the Mitsubishi Colt.
No known weaknesses documented.
Solid Mitsubishi three-cylinder, identical to the Mitsubishi Colt unit. Adequately powered for the small ForFour. Few known issues; typical age-related wear on 20-year-old vehicles.
- !! Timing chain stretched from 120,000 km
The timing chain of the 3A91 can stretch, especially when oil changes are neglected. One forum case was documented at just 53,000 km. Repair costs approx. €1,400.
Symptoms: Metallic rattling on cold start, engine running rough as if on two cylinders, engine warning light, engine cutting out while driving - !! Valve clearance drifts out of spec from 100,000 km
The 3A91 Mitsubishi engine requires a valve clearance check at 100,000 km and adjustment if necessary. If this is missed, engine running deteriorates and fuel consumption rises.
Symptoms: Ticking noises from the valvetrain, rough idle, increased fuel consumption, poorer throttle response - !! Clutch actuator and premature clutch wear from 100,000 km
The automated transmission of the 451 wears the clutch significantly faster than a manual gearbox. By 100,000 km the second clutch is often due.
Symptoms: Jerking when pulling away, delayed clutch engagement, shifting problems, MHD function unreliable
+ 1 more engine weaknesses + vehicle weaknesses
The best engine in the ForFour 454. Mitsubishi 4A90 four-cylinder — reliable, sufficient power, no serious weaknesses known. Identical to the Mitsubishi Colt 1.3. The recommended choice for the ForFour.
- !! Timing chain stretches with neglected oil changes from 95,000 km
The timing chain of the three-cylinder can rattle from 80,000 km with poor oil maintenance. One forum report shows rattling at 95,000 km after 50–60 k km on the same oil. Rare with regular servicing.
Symptoms: Rattling on cold start, metallic clattering from the engine bay, engine warning light with advanced wear - ! Sump gasket leaking — bonded sheet-metal sump from 50,000 km
The sump is made of thin sheet metal and only sealed with sealant compound. From around 40,000 km the seal can start leaking. Oil collects underneath and drips when parked.
Symptoms: Oil patches under the vehicle, oil-coated sump, oil film on the exhaust, dropping oil level - ! Plastic oil filter cap cracks from 40,000 km
The threaded oil filter cap is made of plastic and can develop hairline cracks if over-torqued. Massive oil loss, including oil smeared across the exhaust and rear bumper on the motorway.
Symptoms: Severe oil loss, oil film on exhaust and rear bumper, oil smell, rapidly dropping oil level
+ 1 more engine weaknesses + vehicle weaknesses
The 1.5L four-cylinder from Mitsubishi comes as a standard version (80 kW) and as a Brabus variant (up to 130 kW with turbo). The standard version is reliable; the Brabus version is sporty but puts the drivetrain and clutch under considerable strain.
- !! Wastegate actuator faulty — moisture destroys crown gear from 40,000 km
Moisture enters the plastic housing of the electronic wastegate actuator. Green corrosion on the contacts and broken teeth on the crown gear prevent the valve from closing — no boost pressure.
Symptoms: Yellow engine warning light, no boost pressure, severe power loss, limp mode, sometimes limited to 30 km/h - !! Turbocharger total failure at just 20,000 km from 30,000 km
Some turbochargers fail completely at very low mileage. Workshop diagnoses a faulty turbo; official replacement costs around €2,500 at a Smart dealer.
Symptoms: No throttle response, complete power loss, engine warning light, strong whistling/whining from the turbo area - !! Twinamic dual clutch wears — harsh shifting and judder from 80,000 km
The 6-speed dual-clutch gearbox (Twinamic) shifts harshly and judders on engagement. Crawling in 2nd gear is particularly hard on the clutch as it slips continuously.
Symptoms: Harsh shifting, juddering on pull-away, vibrations at low speeds, clutch smell in stop-and-go traffic
+ 1 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Sills and Wheel Arches Rust The sills and wheel arch edges of the ForFour 454 are regularly affected by rust on older vehicles, as stone chips and moisture attack quickly. Frequent city use and lack of underbody maintenance accelerate the problem. Symptoms: Rust bubbles on sills and wheel arch edges, visible rust-through, paint flaking from 90,000 km | Medium | |
| Exhaust System Corrodes The ForFour 454 exhaust system rusts primarily at the rear silencer due to typical short-trip city use. Condensation water collects in the silencer and corrodes the steel from the inside. A complete replacement can be due before 80,000 km. Symptoms: Visible rust on the rear silencer, holes in the silencer, increased noise, rattling from 70,000 km | Low |
Test Reports
ADAC Gebrauchtwagen-Test Smart ForFour 454
The first Smart ForFour 454 is overall unremarkable according to ADAC — as the sister model of the Mitsubishi Colt it shares its solid basic construction. In the breakdown statistics only the battery stands out as a notable weak point.
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Known Problems and Issues +
A total of 22 weaknesses have been documented for the Smart ForFour 454 (2004–2006) — 12 engine-related and 10 vehicle-related. One problem engine: 4A91 (1.5L). Typical issues affect Rust, Suspension, Electronics, Steering. Considered reliable: 4A90 (1.3L).
ForFour (3A91, 2004–2006) — Be Careful: Timing chain stretched, Valve clearance drifts out of spec, Clutch actuator and premature clutch wear. Power: 64 PS.
ForFour (3A91, 2004–2006) — Be Careful: Timing chain stretched, Valve clearance drifts out of spec, Clutch actuator and premature clutch wear. Power: 75 PS.
ForFour (4A91, 2004–2006) — Stay Away!: Wastegate actuator faulty — moisture destroys crown gear, Turbocharger total failure at just 20,000 km, Twinamic dual clutch wears — harsh shifting and judder. Power: 109 PS.
ForFour (4A91, 2005–2006) — Stay Away!: Wastegate actuator faulty — moisture destroys crown gear, Turbocharger total failure at just 20,000 km, Twinamic dual clutch wears — harsh shifting and judder. Power: 177 PS.
What to watch out for with the Smart ForFour? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Smart ForFour 454 have? +
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Last updated: February 2026 · All information without guarantee